What is yellow fever

Yellow fever is a serious viral hemorrhagic disease caused by the Yellow fever virus that is spread by mosquitoes (Aedes and Haemagogus mosquitos) ¹,². The “yellow” in the name refers to the jaundice (a condition in which your skin and the whites of the eyes become yellow and urine darkens) that affects some patients. The Yellow fever virus is found in tropical and subtropical areas of Africa, South America, Central America and the Caribbean. Currently, 47 countries in Africa and Central and South America are either endemic for, or have regions that are endemic for, yellow fever, with about 200 000 severe cases of Yellow fever worldwide each year and up to 60,000 deaths (see maps of Yellow fever endemic countries below) ¹, ³. In 2015 and 2016, large Yellow fever outbreaks occurred in Angola and the Democratic Republic of the Congo, followed by outbreaks in Brazil and Nigeria in 2017 and 2018. There is no medicine to treat or cure Yellow fever infection. To prevent getting sick from yellow fever, use insect repellent, wear long-sleeved shirts and long pants, and get vaccinated.

Yellow fever virus is spread to people by the bite of an infected mosquito. Yellow fever is a very rare cause of illness in U.S. travelers. The incubation period ranges from 3 to 6 days. Many people do not experience symptoms, but when they occur the most common are fever, muscle pain with prominent backache, headache, loss of appetite, and nausea or vomiting. In most cases, symptoms clear after 3 to 4 days. A small proportion of cases progress to the toxic phase with systemic infection affecting the liver and kidneys. These individuals can have more severe symptoms of high-grade fever, abdominal pain with vomiting, jaundice and dark urine caused by acute liver and kidney failure. Bleeding can occur from the mouth, nose, eyes, or stomach. Death can occur within 7 – 10 days in about half of cases with severe symptoms. Fortunately, there is an effective Yellow fever vaccine for travelers to endemic areas ⁴. A safe and effective Yellow fever vaccine has been available for more than 80 years ⁴. A single dose provides lifelong protection for most people. Other than vaccination, prevention of mosquito bites is the best way to avoid contracting the Yellow fever virus ⁵.

Yellow fever is diagnosed based on laboratory testing, a person’s symptoms and travel history to an endemic area (Africa, South America, Central America and the Caribbean) and exposure to infected mosquitoes, Yellow fever vaccination history. Most Yellow fever cases are self-limited and resemble many other common viral infections. Of those who develop severe disease mortality can approach 50% ⁶. Unlike many other mosquito-transmitted viruses, infected humans are not dead-end hosts and may infect mosquitoes during periods of viremia and spread the virus ⁶.

Yellow fever symptoms

During the first three to six days after you’ve being infected with yellow fever — the incubation period — you won’t experience any signs or symptoms. After this, the infection enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.

Yellow fever symptoms include:

• a high temperature (fever) of 100.4 °F (38 °C) or above
• a headache
• feeling sick or vomiting
• muscle pain and backache
• your eyes being sensitive to light
• loss of appetite and feeling generally unwell

Most people make a full recovery after three or four days.

A few people go on to get more serious symptoms, such as:

• yellowing of the skin and eyes (jaundice)
• bleeding from the mouth, nose or eyes
• vomiting blood or blood in poop

Up to half of those who get serious symptoms die.

There’s no cure nor specific antiviral therapy for yellow fever, but the symptoms can be treated while your body fights off the infection. As a result, treatment consists primarily of supportive care in a hospital. This includes providing fluids and oxygen, maintaining adequate blood pressure, replacing blood loss, providing dialysis for kidney failure, and treating any other infections that develop. Some people receive transfusions of plasma to replace blood proteins that improve clotting.

Most people make a full recovery after three or four days.

If you have yellow fever, your doctor will likely recommend that you stay inside, away from mosquitoes, to avoid transmitting the disease to others. Once you’ve had yellow fever, you’ll be immune to the disease for the rest of your life.

There’s no antiviral medications have proved helpful in treating yellow fever virus infection. But getting a yellow fever vaccine before traveling to an area in which the virus is known to exist can protect you from the disease.

• The yellow fever vaccine can stop you from getting Yellow Fever if you’re traveling to an area where the infection is found.
• Yellow Fever Vaccine Locations (https://wwwnc.cdc.gov/travel/yellow-fever-vaccination-clinics/search)

The yellow fever vaccine is recommended if you’re traveling to:

• an area where yellow fever is found
• a country that requires you to have a certificate proving you’ve been vaccinated against yellow fever

You need to have the vaccine at least 10 days before traveling to give it enough time to work. Your certificate will only be valid after this time.

The yellow fever vaccine is given as an injection into your upper arm.

But even if you’ve been vaccinated, it’s important to prevent insect bites as mosquitoes can also spread other serious illnesses.

Figure 1. Yellow fever virus

Figure 2. Yellow fever mosquito (Aedes aegypti mosquito)

Figure 3. Yellow fever endemic countries – Africa

Footnotes: Map is current as of August 2018. This map is an updated version of the 2010 map created by the Informal WHO Working Group on the Geographic Risk of Yellow Fever. Yellow fever vaccination is generally not recommended in areas where there is low potential for yellow fever virus exposure. However, vaccination might be considered for a small subset of travelers to these areas who are at increased risk for exposure to yellow fever virus because of prolonged travel, heavy exposure to mosquitoes, or inability to avoid mosquito bites. Consideration for vaccination of any traveler must take into account the traveler’s risk of being infected with yellow fever virus, country entry requirements, and individual risk factors for serious vaccine-associated adverse events (e.g., age, immune status).

[Source ⁷ ]

Figure 4. Yellow fever endemic countries – South America

Footnotes: Map is current as of August 2018. This map is an updated version of the 2010 map created by the Informal WHO Working Group on the Geographic Risk of Yellow Fever. In 2017, the Centers for Disease Control and Prevention (CDC) expanded yellow fever vaccination recommendations for travelers to Brazil due to large outbreaks of yellow fever in multiple states within that country. Please refer to CDC’s Travel Health Notices (https://wwwnc.cdc.gov/travel/notices) for more information and updated recommendations. Yellow fever vaccination is generally not recommended in areas where there is low potential for yellow fever virus exposure. However, vaccination might be considered for a small subset of travelers to these areas who are at increased risk for exposure to yellow fever virus because of prolonged travel, heavy exposure to mosquitoes, or inability to avoid mosquito bites. Consideration for vaccination of any traveler must take into account the traveler’s risk of being infected with yellow fever virus, country entry requirements, and individual risk factors for serious vaccine-associated adverse events (such as age or immune status).

[Source ⁸ ]

Yellow fever key facts

• There is no medicine to treat or cure infection from yellow fever.
• Rest, drink fluids, and use pain relievers and medication to reduce fever and relieve aching.
• Avoid certain medications, such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), for example ibuprofen (Advil, Motrin), or naproxen (Aleve), which may increase the risk of bleeding.
• People with severe symptoms of yellow fever infection should be hospitalized for close observation and supportive care.
• If after returning from travel you have symptoms of yellow fever (usually about a week after being bitten by an infected mosquito), protect yourself from mosquito bites for up to 5 days after symptoms begin. This will help prevent spreading yellow fever to uninfected mosquitoes that can spread the virus to other people.
• The yellow fever vaccine can stop you from getting Yellow Fever if you’re traveling to an area where the infection is found.
• Yellow Fever Vaccine Locations (https://wwwnc.cdc.gov/travel/yellow-fever-vaccination-clinics/search)
• A single dose of yellow fever vaccine is sufficient to grant sustained immunity and life-long protection against yellow fever disease. A booster dose of the vaccine is not needed ¹. Yellow fever vaccine provides effective immunity within 10 days for 80-100% of people vaccinated, and within 30 days for more than 99% of people vaccinated ¹.
• Yellow fever vaccine provides protection to >95% of those who are vaccinated and the immunity lasts a lifetime for many ⁹.
• The yellow fever vaccine has been associated with rare occurrences of severe attack on the liver, the kidneys or on the nervous system, estimated to occur at the rates of 0.3 and 0.8 per 100,000 doses distributed, respectively ¹⁰. The risk rises with increasing age and has led to a hesitancy to administer the yellow fever vaccine to persons aged 60 years and older ¹¹. The risk of adverse events following vaccination is also higher for anyone with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or who have a thymus disorder ⁵.

Where does yellow fever virus occur?

Yellow fever virus is found in tropical and subtropical areas in South America and Africa. Yellow fever virus is a very rare cause of illness in U.S. travelers to these areas.

How soon do people get sick after being bitten by an infected mosquito?

The incubation period (time from infection to illness) is usually 3-6 days.

Will I have to go to a special clinic to get a yellow fever vaccination?

Yes. Yellow fever vaccine is regulated by International Health Regulations, so only authorized providers can administer the vaccine. Most providers of yellow fever vaccine can also give you other vaccines or medicines for travel. To find an authorized yellow fever vaccination clinic, see the list of Yellow Fever clinics at https://wwwnc.cdc.gov/travel/yellow-fever-vaccination-clinics/search.

Is yellow fever contagious?

No. Yellow fever is a virus spread by mosquito bites. You can’t get it from close contact with someone who has it.

The mosquitoes acquire the Yellow fever virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human). The mosquitoes transmit the virus back and forth between monkeys, humans or both.

When a mosquito bites a human or a monkey infected with yellow fever, the virus enters the mosquito’s bloodstream and circulates before settling in the salivary glands. When the infected mosquito bites another monkey or human, the virus then enters the host’s bloodstream, where it may cause illness.

If you’re traveling to an area where yellow fever is found, try to avoid being bitten – even if you’ve been vaccinated – as mosquitoes can also spread other serious illnesses, such as malaria and dengue.

You can do this by using mosquito nets, wearing clothes that cover your arms and legs, and using insect repellent containing 50% DEET.

Use Environmental Protection Agency (EPA)-registered insect repellents (https://www.epa.gov/insect-repellents) with one of the active ingredients below. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women.

• DEET
• Picaridin (known as KBR 3023 and icaridin outside the US)
• IR3535
• Oil of lemon eucalyptus (OLE)
• Para-menthane-diol (PMD)
• 2-undecanone

What are the symptoms of yellow fever?

Initial symptoms of yellow fever include sudden onset of fever, chills, severe headache, back pain, general body aches, nausea and vomiting, fatigue, and weakness. Most people improve after these initial symptoms. However, roughly 15% of people will have a brief period of hours to a day without symptoms and will then develop a more severe form of yellow fever disease. In severe cases, a person may develop high fever, jaundice (a condition that involves yellow discoloration of the skin and the whites of the eyes), bleeding (especially from the gastrointestinal tract), and eventually shock and failure of many organs. Roughly 20-50% of people who develop severe illness may die.

How is yellow fever diagnosed?

Yellow fever diagnosis is usually based on blood tests that look for virus or antibodies that a person’s immune system makes against the viral infection.

Yellow fever complications

Yellow fever results in death for 30 to 60 percent of those who develop severe disease. Complications during the toxic phase of a yellow fever infection include kidney and liver failure, jaundice, delirium, and coma.

People who survive the infection recover gradually over a period of several weeks to months, usually without significant organ damage. During this time a person may experience fatigue and jaundice. Other complications include secondary bacterial infections, such as pneumonia or blood infections.

What is the treatment for yellow fever?

No specific treatments have been found to help patients with yellow fever. If possible, patients with yellow fever should be hospitalized for treatment of their symptoms and closely observed by healthcare workers. Rest, fluids, and use of pain medications and fever-reducing medications may relieve symptoms of fever and aching. Certain medications should be avoided, such as aspirin or other non-steroidal anti-inflammatory drugs (such as ibuprofen and naproxen), because these may increase the risk for bleeding.

Yellow fever vaccine

Vaccination is the most important means of preventing yellow fever. The yellow fever vaccine has been available for more than 80 years and it’s safe and a single dose provides life-long protection against yellow fever disease. A booster dose of yellow fever vaccine is not needed.

However, there have been rare reports of serious side-effects from the yellow fever vaccine. The rates for these severe ‘adverse events following immunization’, when the yellow fever vaccine provokes an attack on the liver, the kidneys or on the nervous system are between 0 and 0.21 cases per 10,000 doses in regions where yellow fever is endemic, and from 0.09 to 0.4 cases per 10,000 doses in populations not exposed to the virus ¹², ¹³. The risk of adverse events following immunization is higher for people over 60 years of age and anyone with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or who have a thymus disorder. People over 60 years of age should be given the vaccine after a careful risk-benefit assessment.

Do not donate blood for 14 days after vaccination, because there is a risk of passing vaccine virus to others during that period.

In the United States, the Yellow Fever Vaccine, YF-VAX ¹⁴, is available for purchase by authorized YF-VAX providers. YF-VAX is a vaccine used for the prevention of yellow fever in persons 9 months of age and older (9 months through 59 years of age) in the following categories: persons living in or traveling to yellow fever endemic areas, persons traveling internationally through countries with yellow fever, and laboratory personnel who handle virulent yellow fever virus or concentrated preparations of the yellow fever vaccine virus strains ¹⁵, ¹⁶.

Yellow fever vaccine may be required for entry into certain countries. For vaccination requirements and recommendations for specific countries visit the CDC Travelers’ Health page (https://wwwnc.cdc.gov/travel/destinations/list). Talk to your healthcare provider to determine if you need a yellow fever vaccination or a booster shot before your trip to an area at risk for yellow fever.

After getting the Yellow Fever Vaccine, you will be given an “International Certificate of Vaccination or Prophylaxis” (sometimes called the “yellow card”). You will need this card as proof of vaccination to enter certain countries. If you don’t have it, you might be required to get yellow fever vaccine upon entering the country, or be forced to wait for up to 6 days to make sure you are not infected.

In 2016, the International Health Regulations were officially amended to specify that a completed International Certificate of Vaccination or Prophylaxis (“yellow card”) is valid for the lifetime of the vaccinee, and countries cannot require proof of revaccination (booster) against yellow fever as a condition of entry, even if the last vaccination was >10 years prior ¹⁷. Although booster doses of Yellow fever vaccine are not recommended for most travelers, and despite the recent changes to the International Health Regulations ⁹, clinicians and travelers should nonetheless review the entry requirements for destination countries ¹⁸.

Note: Some countries may require arriving travelers to show proof of yellow fever vaccination. Countries do this as a public health measure to keep travelers from importing the virus. Proof of vaccination requirements may apply to some or all arriving travelers.

Who should have the yellow fever vaccine?

Yellow fever vaccine is recommended for people who are 9 months old or older (9 months through 59 years of age) and who are traveling to or living in areas at risk for yellow fever virus:

• an area where yellow fever is found – including most of sub-Saharan Africa, most of South America, and parts of Central America and the Caribbean
• a country that requires you to have a certificate proving you’ve been vaccinated against yellow fever

You should be vaccinated at least 10 days before you travel to allow enough time for the vaccine to work.

For most people, a single dose of yellow fever vaccine provides long-lasting protection and a booster dose of the vaccine is not needed. However, travelers going to areas with ongoing outbreaks may consider getting a booster dose of yellow fever vaccine if it has been 10 years or more since they were last vaccinated. Certain countries might also require a booster dose of the vaccine; visit CDC’s Travelers’ Health for information on specific country requirements (https://wwwnc.cdc.gov/travel).

Some people might not be able to have the vaccine because there’s a risk it could make them unwell.

Side effects of the yellow fever vaccine

The yellow fever vaccine can cause some side effects, but the risk of not being vaccinated usually outweighs the risk of having side effects.

After having the vaccine, up to one in every three people gets:

• a headache
• muscle pain
• a mild fever
• soreness at the injection site

These side effects usually pass within two weeks. Get medical advice if you feel very unwell within a few days or weeks of having the yellow fever vaccine.

There are also some more serious but very rare side effects that can occur, including an allergic reaction or anaphylaxis and problems affecting the brain (yellow fever vaccine-associated neurologic disease [YEL-AND]) or organs (yellow fever vaccine-associated viscerotropic disease [YEL-AVD]). These occur less than 10 times for every million doses of vaccine given ⁹.

• Serious adverse events. Nine observational studies provided data on serious adverse events for 333 million distributed doses of yellow fever vaccine ¹⁹. Overall, 1,255 persons were reported to have a serious adverse event after yellow fever vaccination. For most (84%) persons, it was unknown if the adverse event occurred after a primary or booster dose of the vaccine. Of the 201 persons with a serious adverse event where dose type was known, 14 (7%) of the adverse events occurred after a booster dose of vaccine.
• Yellow fever vaccine-associated neurologic disease. Eight observational studies provided neurologic disease data for approximately 462 million distributed doses of yellow fever vaccine ¹⁹. A total of 218 persons had yellow fever vaccine–associated neurologic disease. Of the 110 persons where dose type was known, three (3%) persons reported neurologic disease after receiving a booster dose of the vaccine.
• Yellow fever vaccine-associated viscerotropic disease. Eight observational studies provided data on viscerotropic disease for 437 million distributed doses of yellow fever vaccine ¹⁹. A total of 72 persons had yellow fever vaccine–associated viscerotropic disease. Of the 31 persons where dose type was known, one (3%) had viscerotropic disease after receiving a booster dose of the vaccine; no laboratory testing to assess vaccine causality was performed for that case.

How long the yellow fever vaccine lasts?

The yellow fever vaccine provides lifelong protection for most people.

Booster doses and new vaccination certificates used to be recommended every 10 years for people who continued to be at risk of the infection, but this is no longer necessary in most cases.

All yellow fever vaccination certificates are now valid for life, including older ones with an expiry date on them.

Booster doses are usually only recommended if all the following apply ⁹:

• Woman who were pregnant when first vaccinated
• Persons who received a hematopoietic stem cell transplant following their last dose of yellow fever vaccine
• Persons who are HIV-infected
• Travelers who received yellow fever vaccine at least 10 years previously and who will be in a higher-risk setting based on season, location, activities, and duration of their travel
• Laboratory workers who routinely handle wild-type yellow fever virus

Contact a yellow fever vaccination center for advice if you’re not sure if you need a booster dose before traveling.

Who can’t have the yellow fever vaccine?

The yellow fever vaccine isn’t always recommended for some people, including ²⁰:

• People who are very allergic to any of the ingredients in the vaccine – including people with an egg allergy
• Babies under nine months of age – babies who are six to nine months old may sometimes be vaccinated if the risk of getting yellow fever is high
• Pregnant and breastfeeding women
• People over the age of 60
• People with weakened immune systems – such as those with HIV
• People showing symptoms of HIV infection or CD4+ T-lymphocytes less than 200/mm³ (less than 15% of total lymphocytes in children aged 6 years or younger)
• Organ transplant recipients
• People diagnosed with a malignant tumor
• Diagnosed with thymus disorder associated with abnormal immune function
• Diagnosed with a primary immunodeficiency
• Using immunosuppressive and immunomodulatory therapies

Contact a yellow fever vaccination center for advice if you need a vaccination certificate for the country you’re visiting but you’re not sure if you can have the vaccine.

• Yellow Fever Vaccine Locations (https://wwwnc.cdc.gov/travel/yellow-fever-vaccination-clinics/search)

They may provide you with an exemption letter, which may be accepted by officials in countries that usually require a vaccination certificate.

Take extra care to prevent insect bites while traveling if you haven’t been vaccinated.

Yellow fever vaccination certificate

Some countries require a certificate showing you’ve been vaccinated before you’re allowed entry – this is known as an International Certificate of Vaccination or Prophylaxis (sometimes called the “yellow card”).

You’ll be given a certificate when you’re vaccinated at a yellow fever vaccination center.

Check the country information on the Travel Health Pro website (https://travelhealthpro.org.uk/countries) or with a yellow fever vaccination center to see if you need a certificate for the area you’re visiting. A certificate isn’t required for entry into the US, UK, Europe, Asia, Australia, New Zealand or the Pacific Islands.

If you lose your certificate, you may be able to get another one reissued if you have details of the vaccination batch number and the date you had the vaccination.

Does the yellow fever vaccine contain thimerosal?

No, the FDA-approved yellow fever vaccine does not contain thimerosal.

What causes yellow fever?

Yellow fever is caused by a yellow fever virus that is spread by the Aedes aegypti mosquito or Haemagogus species mosquitoes. These mosquitoes thrive in and near human habitations where they breed in even the cleanest water. Most cases of yellow fever occur in sub-Saharan Africa and tropical South America.

These mosquitoes acquire the yellow fever virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human). People infected with yellow fever virus are infectious to mosquitoes (referred to as being “viremic”) shortly before the onset of fever and up to 5 days after onset.

Humans and monkeys are most commonly infected with the yellow fever virus. Mosquitoes transmit the virus back and forth between monkeys, humans or both. Person to person or primate to human transmission has not been reported without the involvement of a mosquito vector ²¹.

When a mosquito bites a human or a monkey infected with yellow fever, the virus enters the mosquito’s bloodstream and circulates before settling in the salivary glands. When the infected mosquito bites another monkey or human, the virus then enters the host’s bloodstream, where it may cause illness.

Yellow fever virus is an RNA virus that belongs to the genus Flavivirus, closely related to the viruses that cause West Nile, St. Louis encephalitis and Japanese encephalitis ⁶.

Risk factors for getting yellow fever

You may be at risk of the disease if you travel to an area where mosquitoes continue to carry the yellow fever virus. These areas include sub-Saharan Africa and tropical South America.

Even if there aren’t current reports of infected humans in these areas, it doesn’t mean you’re risk-free. It’s possible that local populations have been vaccinated and are protected from the disease, or that cases of yellow fever just haven’t been detected and officially reported.

If you’re planning on traveling to these areas, you can protect yourself by getting a yellow fever vaccine at least several weeks before traveling.

Anyone can be infected with the yellow fever virus, but older adults are at greater risk of getting seriously ill.

How is yellow fever spread?

Yellow fever is a virus spread by mosquito bites. You can’t get it from close contact with someone who has it.

The mosquitoes (Aedes aegypti mosquito or Haemagogus species mosquitoes) that spread the infection are found in towns and rural areas. They mainly bite during the day.

If you’re traveling to an area where yellow fever is found, try to avoid being bitten – even if you’ve been vaccinated – as mosquitoes can also spread other serious illnesses, such as malaria and dengue.

You can do this by using mosquito nets, wearing clothes that cover your arms and legs, and using insect repellent containing 50% DEET.

Yellow fever virus has three transmission cycles:

1. Jungle (sylvatic) cycle. The jungle (sylvatic) cycle involves transmission of the virus between non-human primates (e.g., monkeys) and mosquito species found in the forest canopy. The virus is transmitted by mosquitoes from monkeys to humans when humans are visiting or working in the jungle.
2. Inter­mediate (savannah) cycle. In Africa, an intermediate (savannah) cycle exists that involves transmission of virus from mosquitoes to humans living or working in jungle border areas. In this cycle, the virus can be transmitted from monkey to human or from human to human via mosquitoes.
3. Urban cycle. The urban cycle involves trans­mission of the virus between humans and urban mosquitoes, primarily Aedes aegypti. The virus is usually brought to the urban setting by a viremic human who was infected in the jungle or savannah.

Figure 5. Yellow fever transmission cycle

[Source ²² ]

Yellow fever prevention

The most effective way to prevent infection from Yellow Fever virus is to prevent mosquito bites and get Yellow Fever vaccination. Mosquitoes bite during the day and night. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and get vaccinated before traveling, if vaccination is recommended for you.

Yellow Fever vaccine

A highly effective vaccine exists to prevent yellow fever. Yellow fever is known to be present in sub-Saharan Africa and parts of South America. If you live in one of these areas, talk to your doctor about whether you need the yellow fever vaccine. If you plan to travel in these areas, talk with your doctor at least 10 days, but preferably three to four weeks, before your trip begins. Some countries require travelers to present a valid certificate of immunization upon entry.

A single dose of the yellow fever vaccine provides protection for at least 10 years. Side effects are usually mild, lasting five to 10 days, and may include headaches, low-grade fevers, muscle pain, fatigue and soreness at the site of injection. More-significant reactions — such as developing a syndrome similar to actual yellow fever, inflammation of the brain (encephalitis) or death — can occur, most often in infants and older adults. The vaccine is considered safest for those between the ages of 9 months and 60 years.

Talk to your doctor about whether the yellow fever vaccine is appropriate if your child is younger than 9 months, if you have a weakened immune system (immunocompromised), are pregnant or if you’re older than 60 years.

Prevent Mosquito Bites

Use Insect Repellent

List of insect repellant products approved by the EPA : https://www.epa.gov/insect-repellents/find-repellent-right-you

Use Environmental Protection Agency (EPA)-registered insect repellents with one of the active ingredients below. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women.

• DEET
• Picaridin (known as KBR 3023 and icaridin outside the US)
• IR3535
• Oil of lemon eucalyptus (OLE)
• Para-menthane-diol (PMD)
• 2-undecanone

Tips for babies and children

• Always follow instructions when applying insect repellent to children.
• Do not use insect repellent on babies younger than 2 months old.
• Instead, dress your child in clothing that covers arms and legs.
• Cover strollers and baby carriers with mosquito netting.
• Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under 3 years old.
• Do not apply insect repellent to a child’s hands, eyes, mouth, cuts, or irritated skin.
  • Adults: Spray insect repellent onto your hands and then apply to a child’s face.

Tips for Everyone

• Always follow the product label instructions.
• Reapply insect repellent as directed.
• Do not spray repellent on the skin under clothing.
• If you are also using sunscreen, apply sunscreen first and insect repellent second.

Natural insect repellents (repellents not registered with EPA)

• Experts do not know the effectiveness of non-EPA registered insect repellents, including some natural repellents.
• To protect yourself against diseases spread by mosquitoes, CDC and EPA recommend using an EPA-registered insect repellent.
• Choosing an EPA-registered repellent ensures the EPA has evaluated the product for effectiveness.
• Visit the EPA website to learn more (https://www.epa.gov/insect-repellents).

Protect your baby or child

• Dress your child in clothing that covers arms and legs.
• Cover crib, stroller, and baby carrier with mosquito netting.

Wear long-sleeved shirts and long pants

Treat clothing and gear:

• Use permethrin to treat clothing and gear (such as boots, pants, socks, and tents) or buy permethrin-treated clothing and gear.
• Permethrin is an insecticide that kills or repels mosquitoes.
• Permethrin-treated clothing provides protection after multiple washings.
• Read product information to find out how long the protection will last.
• If treating items yourself, follow the product instructions.

Do NOT use permethrin products directly on skin.

Take steps to control mosquitoes indoors and outdoors:

• Use screens on windows and doors. Repair holes in screens to keep mosquitoes outdoors.
• Use air conditioning, if available.
• Stop mosquitoes from laying eggs in or near water.
• Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.
• Check indoors and outdoors.

Prevent mosquito bites when traveling overseas:

• Choose a hotel or lodging with air conditioning or screens on windows and doors.
• Sleep under a mosquito bed net if you are outside or in a room that does not have screens.
• Buy a bed net at your local outdoor store or online before traveling overseas.
• Choose a WHOPES-approved bed net: compact, white, rectangular, with 156 holes per square inch, and long enough to tuck under the mattress.
• Permethrin-treated bed nets provide more protection than untreated nets.
  • Do not wash bed nets or expose them to sunlight. This will break down the insecticide more quickly.

The following can reduce your risk of being bitten:

• use insect repellent – products containing 50% DEET are most effective, but lower concentrations (15-30% DEET) should be used in children, and alternatives to DEET should be used in children younger than two months
• wear loose but protective clothing – mosquitoes can bite through tight-fitting clothes; trousers, long-sleeved shirts, and socks and shoes (not sandals) are ideal
• sleep under a mosquito net – ideally one that has been treated with insecticide
• be aware of your environment – mosquitoes that spread Yellow Fever virus breed in standing water in urban areas
• stay in air-conditioned or well-screened housing. The mosquitoes that carry the Yellow Fever virus are most active from dawn to dusk, but they can also bite at night.

It’s a good idea to speak to your doctor, practice nurse or a travel clinic before traveling to get specific advice about what you can do to avoid Yellow Fever virus (e.g., Yellow Fever vaccination) and other travel illnesses.

Yellow fever symptoms

The majority of people infected with yellow fever virus will either not have symptoms, or have mild symptoms and completely recover.

For people who develop symptoms, the time from infection until illness is typically 3 to 6 days.

Because there is a risk of severe disease, all people who develop symptoms of yellow fever after traveling to or living in an area at risk for the virus should see their healthcare provider. Once you have been infected, you are likely to be protected from future infections.

Yellow fever symptoms:

• Most people infected with yellow fever virus will either have no symptoms or mild symptoms and completely recover.

Acute phase

• Some people will develop yellow fever illness with initial symptoms including:
  • Sudden onset of fever
  • Chills
  • Severe headache
  • Back pain
  • General body aches
  • Muscle aches, particularly in your back and knees
  • Sensitivity to light
  • Loss of appetite
  • Dizziness
  • Red eyes, face or tongue
  • Nausea
  • Vomiting
  • Fatigue (feeling tired)
  • Weakness
  • Most people with the initial symptoms improve within one week.
  • For some people who recover, weakness and fatigue (feeling tired) might last several months.

Toxic phase

Although signs and symptoms may disappear for a day or two following the acute phase, some people with acute yellow fever then enter a toxic phase. During the toxic phase, acute signs and symptoms return and more-severe and life-threatening ones also appear.

• A few people will develop a more severe form of the disease.
  • For 1 out of 7 people who have the initial symptoms, there will be a brief remission (a time you feel better) that may last only a few hours or for a day, followed by a more severe form of the disease.
• Severe symptoms include:
  • High fever
  • Yellowing of your skin and the whites of your eyes (jaundice)
  • Bleeding from your nose, mouth and eyes
  • Shock
  • Organ failure
  • Abdominal pain and vomiting, sometimes of blood
  • Decreased urination
  • Slow heart rate (bradycardia)
  • Liver and kidney failure
  • Brain dysfunction, including delirium, seizures and coma
• Severe yellow fever disease can be deadly. If you develop any of these symptoms, see a healthcare provider immediately.
• Among those who develop severe disease, 30-60% die.

Yellow fever diagnosis

Diagnosing yellow fever based on signs and symptoms can be difficult because early in its course, the infection can be easily confused with malaria, typhoid, dengue fever and other viral hemorrhagic fevers.

A presumptive diagnosis of yellow fever is often based on the patient’s clinical features, places and dates of travel (if the patient is from a non-endemic country or area), activities, and epidemiologic history of the location where the presumed infection occurred.

To diagnose your condition, your doctor will likely:

• Ask questions about your medical and travel history
• Collect a blood sample for testing

If you have yellow fever, your blood may reveal the virus itself. If not, blood tests also can detect antibodies and other substances specific to the virus.

Diagnostic Testing

Laboratory diagnosis of yellow fever is generally accomplished by testing of serum to detect virus-specific IgM and neutralizing antibodies. Sometimes the virus can be found in blood samples taken early in the illness.

In fatal cases, nucleic acid amplification, histopathology with immunohistochemistry, and virus culture of biopsy or autopsy tissues can also be positive. Only a few state laboratories or other specialized laboratories, including those at Centers for Disease Control and Prevention (CDC), are capable of doing these specialized tests.

Test results are normally available 4 to 14 days after specimen receipt. Reporting times for test results may be longer during summer months when domestic arbovirus activity increases. Receipt of a hard copy of the results will take at least 2 weeks after testing is completed. Initial serological testing will be performed using IgM-capture ELISA, MIA (Microsphere-based Immunoassay) and IgG ELISA. If the initial results are positive, further confirmatory testing may delay the reporting of final results. ALL RESULTS WILL BE SENT TO THE APPROPRIATE STATE HEALTH DEPARTMENT.

Yellow fever treatment

There’s no cure nor specific treatment for yellow fever, but the symptoms can be treated while your body fights off the infection.

Most people make a full recovery after three or four days. Even though yellow fever is not transmitted from person to person, isolation of the individual should be undertaken until the diagnosis is confirmed. Universal precautions are required when looking after patients with yellow fever although person-person transmission of the virus is unlikely. Infected patients should avoid mosquitoes, as they may transmit the virus to mosquitoes, which can serve as vectors for infection other patients.

Painkillers such as acetaminophen (paracetamol) can help lower your temperature and relieve aches or pains in the meantime. Also drink plenty of fluids to avoid dehydration.

Avoid certain medications, such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), for example ibuprofen (Advil, Motrin), or naproxen (Aleve), which may increase the risk of bleeding.

If you have more serious symptoms, you may need to go into hospital for close monitoring and treatment of your symptoms until you’re feeling better.

People who are seriously ill will need to be looked after in the intensive care unit (ICU) and closely monitored for disseminated intravascular coagulation (DIC), hemorrhage, kidney, and liver dysfunction.

Bleeding disorder is managed with fresh frozen plasma, and renal failure may require dialysis.

Yellow fever prognosis

Most yellow fever cases are subclinical or mildly symptomatic with an excellent prognosis ⁶. About 15% of symptomatic patients will develop severe disease. Most will recover, but after a bout of yellow fever, full recovery may take weeks or months. In most cases, there is a reversal of the liver and kidney dysfunction. Death occurs in 30% to 50% of patients with severe disease ⁶. All travelers to endemic areas should be vaccinated if they are candidates for the live attenuated vaccine.

Death often occurs within 2 weeks during the toxic phase of the infection. Unvaccinated travelers to endemic areas are at high risk for developing symptomatic disease compared to the natives, who have acquired immunity.

References

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