Yellow Fever: Symptoms, Causes and Vaccination
Who is at Risk?
Anyone who travels to or resides in a place which is occupied by infected mosquitoes is at risk of getting yellow fever.
There are various factors which determine whether a traveler will or will not get yellow fever. These include destination of travel, immunization status, season, length of exposure, participation in outdoor activities and the level of virus transmission at the time of travel. For example, the raining season is a bad time to travel to rural West Africa or South America, as it is the breeding time for mosquitoes. During this season, the risk of catching yellow fever is high.
Most cases of yellow fever happen in 32 countries of Africa and 13 countries of Latin America. Here’s a list of places which should be on your watch-out list, if you happen to be in or around any of these.
Central and South America
- French Guiana
- Trinidad and Tobago
- Burkina Faso
- Central African Republic
- Republic of the Côte d’Ivoire
- Democratic Republic of the Congo
- Equatorial Guinea
- Sierra Leone
- South Sudan
[Source: CDC, Centers for Disease Control and Prevention]
If you are traveling to Brazil soon, you should know that it is under Level 2 Travel Alert, as per CDC. Since early 2018, multiple unvaccinated travelers (not from US) to Brazil have died due to yellow fever infection.
There are other African countries with a low risk of yellow fever and these are Eritrea, Rwanda, São Tomé and Príncipe, Somalia, Tanzania and Zambia. The risk of getting yellow fever in South Africa is higher than South America where it’s not very likely for people to come in contact with monkeys who might carry the yellow fever virus. Plus, a large number of residents in South American countries use vaccines, thereby reducing the risk of transmission.
Signs and Symptoms
The term yellow fever is a combination of ‘yellow’ and ‘fever’, both of which denote the symptoms of the illness. A person who has contracted yellow fever suffers from high fever and yellowing of the skin.
It may take 3-6 days (incubation period) before the symptoms fully develop. This means you won’t notice symptoms immediately after infection. Once the incubation period is over, the patient will start to experience a number of signs and symptoms, in the early stage and the toxic stage.
First (Early) Stage Symptoms
- Ache in joint and muscles
- Shivers or Chills
Many patients recover at the first stage itself. However, some yellow fever patients show the initial symptoms and then the symptoms disappear. After a gap of 24 hours, the symptoms may arise again, which is called the toxic stage. The toxic stage symptoms are severe and could threaten the lives of patients.
According to a survey by WHO, 20 to 50 percent of patients who enter the toxic stage die within a period of two weeks.
Second (Toxic) Stage Symptoms
- Abdominal pain
- Join aches
- Loss of appetite
- Vomiting, sometimes with blood
- Bleeding from nose
- Kidney, liver failure
- Slow heart rate
- Brain dysfunction
The virus that causes yellow fever is known asflavivirus.
The Aedes aegypti mosquito is the carrier of this virus. The mosquito gets infected after it bites an infected human or monkey.
An infected mosquito carries the virus throughout its lifespan. Monkeys that live in tropical rainforests are believed to have the flavivirus in their blood, particularly in places such as Africa and South America. If a person visits a jungle and gets bitten by an infected mosquito, that person becomes infected and a source of infection for others once back in the community.
When to Visit a Doctor
Early diagnosis helps save the lives of patients. If you have been to a place with a risk of yellow fever and are experiencing symptoms that look like that of flue, you should see a doctor immediately. During consultation, the doctor will ask you several questions to know more about the case. And then, if the doctor gets suspicious that you may have been infected, you’ll be asked to go for a blood test.
It’s only after your blood sample is analyzed, the doctor can be sure whether you have yellow fever virus or not.
Unfortunately, there’s no cure for yellow fever.
If there was an antiviral medication to treat yellow fever, doctors would be able to save so many lives. But there isn’t. Patients suffering from yellow fever have to depend only on supportive care in a hospital.
At the hospital, the doctor only focuses on dealing with the symptoms and improving the efficiency of the immune system in patients. If the immune system responds better, the intensity of the infection reduces. In some cases, the doctor may also use plasma transfusion as a form of treatment. Advice is also given to patients to avoid taking pain killers like aspirin. Use of non-steroidal anti-inflammatory drugs can lead to or increase internal bleeding in yellow fever patients.
Supportive care for patients include:
Getting lots of fluid, possibly through veins
Bringing the blood pressure to normal
Getting blood transfusion
Getting dialysis, in case of kidney failure
Getting treatment for secondary infections
Patients with yellow fever are kept under constant monitoring and observation. The doctor also ensures that the patient doesn’t get a mosquito bite because it would only spread the infection to other people.
Vaccination – The Most Effective Way to Prevent Yellow Fever
Since there’s no cure for yellow fever yet, the only preventive measure that you have is vaccination. The yellow fever vaccine contains the 17D strain (live and attenuated version) of the virus.
A single shot of this vaccine gives you protection for a span of 10 years. The vaccine boosts the immunity of a person within ten days of getting the dose. As suggested by the Centers for Disease Control and Prevention (CDC), the yellow fever vaccine is safe for anyone aged between 9 months and 59 years, except those people who are highly allergic to some food and proteins or have a compromised immune system. If you are over 60 years and you’re traveling to a country which has a risk of yellow fever, you should consult a doctor regarding vaccination.
Where to Get: The US-licensed yellow fever vaccine (YF-VAX) is available at select travel clinics across the United States. Sometimes, all the clinics may not have a good supply of this vaccine and use Stamaril as an alternative. Currently, there can be a shortage of yellow fever vaccine in US, but you can expect it to be widely available again by mid-2019. For more information, you should contact a nearby clinic in your area or visit this page on the CDC website which helps you search for yellow fever vaccination clinics in multiple states of the US. You can also talk to your doctor for details of clinics that provide the vaccine.
Duration: In most cases, the yellow fever vaccine provides protection for a lifetime. For people who have a high risk of getting this viral infection may be recommended to get another booster dose after 10 years of getting the first shot and obtain new vaccination certificates to produce as required.
Cost: Yellow fever vaccine is affordable for everyone. It’s a good idea to obtain a full price list of travel vaccinations from a clinic that’s close to your place.
Side-Effects: Fortunately major side-effects of yellow fever vaccine are uncommon.. Usually some people may experience some mild symptoms like fever, muscle aches and joint pain shortly after the injection. If you have these mild symptoms, there’s nothing to worry about. Usually, these symptoms disappear within a week. In case, there are signs of an allergic reaction after getting the shot, seek medical help urgently. A booster dose of this vaccine is not recommended for people who have experienced fatal allergic reactions like chest tightness, swelling in face and difficult breathing after the first shot. Older adults may be more likely to have serious side-effects.
Other Methods of Prevention
Vaccination is the only way to keep yourself well-protected when entering a country or city that has a risk of yellow fever. However, there are some recommendations that you can use for the prevention of this disease.
- Avoid indulging in outdoor activities in a mosquito-infested area
- Have your arms, hands and legs covered for protection against mosquito bites
- Choose well-screened accommodation for stay during travel
- If your accommodation doesn’t have AC or window screens, use netting over beds
- Use mosquito repellents and other related gear
When you want to keep mosquitoes away, you can either use non-skin repellent or skin repellent. Depending on the situation, you can either apply repellent to your clothing or skin (or both). Due to the presence of chemical ingredients, mosquito repellents can prove to be harmful when used for several hours or days in a row. So, make sure you use mosquito repellents only for the amount of time you’ll be outdoors. Skin repellents should not be used on the hands of infants who are below 2 months of age. Instead, cover their stroller with mosquito netting when outdoors.
9 Facts about Yellow Fever You Should Know
- Yellow fever is a mosquito-borne disease. It’s called yellow fever because of symptoms including yellowing of skin (jaundice) and high fever.
- Common symptoms of yellow fever are headache, fever, joint and muscle aches, nausea, vomiting, loss of appetite, fatigue etc.
- A small percentage of infected patients who enter the toxic stage show severe symptoms and almost half of them die within 1-2 weeks.
- Though there’s no cure for yellow fever yet, the disease can be controlled by managing symptoms and strengthening the immune system of patients.
- There are some countries where entry is prohibited for travelers until they produce their immunization certificates.
- In the past around the 17th and 18th centuries the United States and Europe have witnessed large epidemics of yellow fever, resulting in thousands of deaths.
- The first ever vaccine for the prevention of yellow fever was discovered by Max Theiler in 1951. Dr. Theiler was awarded with the Nobel Prize in Physiology or Medicine for his excellent, life-saving work.
- The yellow fever virus is most common in the tropical areas of Africa and Central and South America. If you’re planning to travel to any of these places, make sure you get vaccinated – at least a month in advance.
- Due to favorable climatic conditions, some parts of Canada too have a high risk of yellow fever infection. So, before you plan a trip to these areas, make sure you are properly informed and vaccinated.
The Bottom Line
Yellow fever is a deadly illness. If you are traveling to an at-risk city or an area where multiple cases of yellow fever have been recorded in the recent past, make sure you get yourself vaccinated before departure.
If you have any questions or doubts, get in touch with a doctor. They’ll explain it all and give you the best advice.
Even after you have been vaccinated, you should never forget to follow other methods of prevention. Throughout the period of your travel, keep yourself protected against mosquito bites. Stay in AC rooms and try to stay indoors when the risk of getting mosquito bites is high. When outdoors, wear protective clothing and use mosquito repellents so that you have a safe travel.