Yellow Fever: Symptoms, Causes & Prevention
Yellow fever is a viral disease, rather infection, spread by infected mosquitoes. Yellow fever symptoms include mild signs like fever or body pain to serious complications like organ failure. It can be prevented by vaccines, and it can also turn fatal at times. In case you are planning to visit regions where yellow fever infection is quite common, you must consult your doctor for travel health advice before setting out for your trip. Read on this blog to find out more yellow fever, its causes, symptoms, diagnosis, treatment, prevention, and vaccination.
What is yellow fever?
An acute viral infection, yellow fever is spread by infected mosquitoes. It leads to developing jaundice in people, resulting in yellowing of the eyes and skin. This infection can be dangerous and might even lead to failure of multiple organs, bleeding from the eyes, mouths, stomach or ears causing haemorrhagic fever, and even death. However, vaccination can be a potential solution for yellow fever management.
How is yellow fever spread?
Yellow fever is usually transmitted through the bite of an infected mosquito, usually female. By biting an infected individual or some other primate and drinking their blood, the mosquitoes come in contact with the virus. If they remain infected while laying eggs, such mosquitoes further pass on the infection to their offspring. The virus of yellow fever lies in the saliva of the infected mosquito; and when it bites another healthy individual the virus is injected into the bloodstream.
Yellow fever transmission occurs through three cycles:
Jungle cycle: Monkeys are the reservoirs of the yellow fever virus in jungles and rainforests. On bitten infected monkeys wild mosquitoes get infected, and then they bite other monkeys; thereby spreading the infection. When humans visit these jungles and rainforests, those infected mosquitoes again bite them and ultimately end up spreading the virus to urban areas.
Intermediate cycle: Also called the savannah cycle, it occurs only in African regions where humans live or work closely to jungles and rainforests. It involves mosquitoes transmitting the virus between monkeys and humans.
Urban cycle: After getting infected in the jungle, humans bring yellow fever virus into cities and towns. Mosquitoes breeding in those urban areas bite those infected humans first and then again bite healthy humans, spreading the infection.
The mosquito aedes aegypti are mainly responsible for transmitting yellow fever. These mosquitoes are mostly found in South America and Africa, but they are also found in other tropical and subtropical regions.
Remember that yellow fever virus cannot be transmitted from one human to other unless they come in direct contact, like sharing contaminated needles.
How do you get yellow fever?
A virus carried by mosquitoes is the main reason for yellow fever. If you are bitten by an infected mosquito, you can develop yellow ever. Although yellow fever can occur in any individual, older people are more prone t the risks of infection. Symptoms usually appear 3 to 6 days after you have been bitten by the infected mosquito.
Symptoms of Yellow Fever
Yellow fever occurs in 3 stages:
- Stage 1 (infection): It is a span of 3 to 4 days when you will experience pain in the muscle and joints, headache, flushing, fever, vomiting, jaundice, and loss of appetite.
- Stage 2 (remission): While symptoms start disappearing at this stage and people usually recover, patients in some cases might get worse in 24 hours.
- Stage 3 (intoxication): It is characterised by problems in liver, kidney, heart, or other organs. Seizures, bleeding disorders, delirium, and coma are some rare signs which may occur.
Some other common yellow fever symptoms include:
- Nausea and vomiting blood
- Redness in the face, tongue, and eyes
- Signs of jaundice, yellow eyes and skin
- Reduced urination
- Arrhythmias, a condition of irregular heartbeats
- Bleeding may progress to haemorrhage
Yellow Fever Diagnosis
Diagnosing yellow fever is not easy, particularly in the early stages. More severe infections are often confused with leptospirosis, malaria, haemorrhagic fevers, viral hepatitis, poisoning, or infection with other flaviviruses like dengue.
Doctor might recommend polymerase chain reaction (PCR) testing – a type of blood test to detect the yellow fever virus during the early stages. Testing with PRNT and ELISA can help diagnose antibodies in the later stages of the disease.
Yellow Fever Treatment
Yellow fever does not have any specific cure as per latest studies. So at present yellow fever treatment typically means the management of symptoms:
Painkillers: Some early signs of yellow fever like muscle pain, headache, or fever can be treated with common medications for fever.
Have plenty of fluids: Yellow fever causes loss of fluids from your body, resulting in dehydration, particularly if you tend to vomit or are feverish. It limits your body’s ability to fight off the yellow fever virus, leading to more severe symptoms. This is you must intake plenty of water and other fluids as well.
Hospital treatment: In cases of severe yellow fever, more advanced symptoms break out, requiring immediate hospital treatment. If you are facing yellow fever symptoms and do not heal within 3 to 6 days, seek medical attention promptly for timely diagnosis and treatment.
Prevention of Yellow Fever
Some tips for preventing yellow fever infection include:
- Vector control: As mosquito bite is the principal cause of yellow fever, safeguarding yourself from mosquito bites can the best way to prevent yellow fever infection. For this you should use insect repellent, treat clothing with permethrin, use mosquito net while sleeping, go for air conditioned and screened rooms, and wear long sleeved pants and shirts to keep your skin covered as much as possible.
Remember that elimination of potential sites where mosquitoes breed can help prevent yellow fever transmission. This can be done by application of larvicides to containers and other places storing water.
- Vaccination: It is the most effective way of preventing yellow fever. It is a safe and affordable option, a single dose of which offers lifetime protection against this infection. Even a booster dose of this vaccine is not needed in most cases.
About 80% to 100% of people receiving yellow fever vaccination develop effective immunity against this infection within 10 days. And over 99% people have been reported to become immune to yellow fever within 30 days after vaccination.
- Preparedness and response to epidemics: Prompt detection of yellow fever and rapid emergency vaccination campaigns are vital for outbreak control. However, underreporting remains a serious concern, with the WHO estimating the actual number of cases to be nearly 10 to 250 times higher than reported.
A confirmed yellow fever case in an unvaccinated population is referred to as an outbreak. Every confirmed case must undergo thorough investigation. Response teams must implement both immediate emergency measures and long term immunisation strategies to control the outbreak effectively.
Yellow Fever Vaccination
The yellow fever vaccine offers protection against infection when travelling to regions where the virus is present, helping prevent the spread of the disease between countries. After receiving the vaccine, travellers are issued a yellow fever vaccine certificate, confirming their immunity. Proof of vaccination is required by countries where yellow fever is endemic or where conditions exist for the virus to spread, such as the presence of specific mosquito and monkey species that could harbour the infection. This certificate helps ensure public health safety during international travel.
The yellow fever vaccine is administered as an injection in the upper arm. Even with vaccination, it is crucial to prevent insect bites, as mosquitoes can transmit other serious diseases.
Who should have the yellow fever vaccine?
For individuals from 9 months of age who are going to travel to the following places, the yellow fever vaccine is recommended:
- Area where yellow fever is common, like parts of sub-Saharan Africa, Central America, South America, and Trinidad in the Caribbean
- A country where your yellow fever vaccination certificate is necessary
Who cannot have the yellow fever vaccine?
Although most people are fit for getting the yellow fever vaccine, the following people should not get the vaccine:
- Babies below 6 months of age
- Individuals having a weak immune system due to treatments with chemotherapy and steroids
- Individuals who experienced severe reactions due to a previous dose of the vaccine
- People over 60 years of age, and travelling to yellow fever areas where vaccine is not compulsory, need not get vaccinated
- People having a close relative who has previously faced a severe reaction to the vaccine, resulting in damage to the brain or other organs
- People suffering from a thymus gland disorder or complete removal of the gland
- People exhibiting allergic reactions against any ingredient in the vaccine, such as an egg allergy
- People with weak immunity like those with lymphoma or leukaemia
If you are unable to receive the yellow fever vaccine in the UK but need a vaccination certificate for travel, contact a yellow fever vaccination centre. They may issue an exemption letter, which some countries may accept in place of a vaccination certificate for entry requirements.
Side Effects of Yellow Fever Vaccine
The yellow fever vaccine may cause side effects, but the risk of not receiving the yellow fever vaccination is more dangerous than the potential side effects. After getting the vaccine, every one in three individuals report muscle pain, headache, soreness in the site of injection, or a raised temperature. However, these side effects usually dissolve in 2 weeks.
Some severe yellow fever side effects such as an allergic reaction to the vaccine or damage to the brain or other organs are quite rare. They mostly attack individuals above 60 years, having a weak immune system, or some problem with the thymus gland. If you continue to feel unwell up to several days after taking the vaccine, seek medical attention at once.
What factors determine your risks of contracting yellow fever?
Several factors influence the risks of contracting yellow fever, such as:
- Your travel destination
- The intensity of yellow fever transmission in your destination area
- The season when you are travelling; the infection is most likely to occur in late rainy season or early dry season
- Duration of travel
- Activities encouraging your exposure to mosquitoes
- Your status of yellow fever immunisation
In order to resist the international spread of yellow fever, countries often demand proof of vaccination.
Complications of Yellow Fever
If left untreated, yellow fever may produce severe complications like:
- Death
- Coma
- Kidney failure
- Disseminated intravascular coagulation (DIC)
- Salivary gland infection (parotitis)
- Liver failure
- Shock
- Secondary bacterial infections
When to see the doctor?
If you develop symptoms of yellow fever while traveling in an area where the virus is present, or have recently returned from such a region, seek medical attention immediately. The doctor will ask about your travel history and specific symptoms to help diagnose whether you have yellow fever and determine the appropriate course of action for treatment.
Final Thoughts
Yellow fever can be fatal, but it is completely preventable with the yellow fever vaccine. To reduce mosquito bites, use repellents and wear protective clothing. Some areas implement mosquito control programs. If you develop symptoms like fever or body aches after visiting areas with yellow fever outbreaks, contact your healthcare provider. Remember, yellow fever is still a threat today, not just a disease of the past.
If you are planning a trip recently to any of the countries discussed above, visit our GP at Private GPs London for your travel health check-up and necessary vaccination for yellow fever.
FAQs
Why is yellow fever named as ‘yellow’?
The term “yellow” is used in the name of the disease – yellow fever; as it refers to jaundice which causes skin to turn yellow. The infection is also typically accompanied by fever, which led to the name “yellow fever”.
Is yellow fever contagious?
Yellow fever is not spread directly from person to person through actions like coughing or kissing. However, if you are infected, a mosquito can bite you and transmit the virus to someone else.
Are yellow fever and malaria the same thing?
Yellow fever and malaria share similarities, such as being mosquito-borne diseases, causing fever, flu-like symptoms, jaundice, severe illness, and even death. However, they have significant differences like malaria is caused by a parasite, while yellow fever by a virus. Different mosquitoes spread each disease, and while a vaccine exists for controlling yellow fever, there is no vaccine for malaria.
Where is yellow fever more common?
Yellow fever is commonly found in tropical and subtropical regions of sub-Saharan Africa, South America, and parts of Central America and the Caribbean. Some countries may require a yellow fever vaccination certificate as proof of immunisation before allowing entry.
Is yellow fever serious?
Yellow fever can be severe, but most people completely recover within 3 to 4 days after experiencing early symptoms. However, if symptoms progress to the ‘toxic phase’ with jaundice, the fatality rate ranges from 20% to 50%. Vaccination is strongly recommended for travellers to destinations with risks of yellow fever.
How long does the effect of yellow fever vaccine last?
The yellow fever vaccine offers lifelong protection for most people. However, additional doses may be recommended for travellers who were previously vaccinated when pregnant, under 2 years old, living with HIV, or had a weakened immune system. Further doses may also be advised for those at higher risk, such as long term travellers.
Where to get yellow fever injection?
You can only get yellow fever vaccines or injections at registered centres of yellow fever vaccination in the UK.
How long before travelling should I get vaccinated for yellow fever?
Getting vaccinated before travelling is essential to protect your health, the health of others, and public health in the communities you visit. For yellow fever, it is recommended to receive the vaccine at least 10 days before departure to ensure immunity and the validity of your ‘International Certificate of Vaccination’.
How much does a yellow fever vaccine cost?
The yellow fever vaccine is not available for free in the UK, not even on the NHS. You need to pay for the vaccine, and the typical average cost ranges between £60 and £85.
