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Diseases & Vaccines / More Vaccine Preventable Diseases / Yellow Fever / Frequently Asked Questions

FREQUENTLY ASKED QUESTIONS: YELLOW FEVER

what is YF?;  what are the symptoms of YF disease?;  why is YF a health problem in the world?;  is YF a serious health problem in South Africa?;  who is at risk?;  how is YF transmitted?;  how do i know if have or have had YF disease?;  what is the treatment following YF infection?;  how is YF prevented?;  who should get the YF vaccine?;  how and when is the YF vaccine given?;  should HIV positive individuals be vaccinated?;  what are the side effects of the YF vaccine?

1.     What is yellow fever (YF)?

YF is an acute systemic disease, prevalent in the tropical regions of Africa and South America, caused by the YF virus (YFV). The disease is so called because of the jaundiced (i.e. yellow) skin that appears in most of the patients.

Symptoms of YF appear after an incubation period of 3 to 6 days. The disease has three phases:

Acute phase lasts for 3 to 4 days and is characterised by:

• Fever
• Malaise
• Myalgia (muscle pain)
• Headache
• Loss of appetite
• Nausea
• Vomiting

Remission phase lasts for up to 48 hours, and in case of abortive infection, the patient completely recovers. However, 15% of cases enter the third stage of the disease which can be fatal.

Toxic phase occurs in those patients where recovery is incomplete and is characterised by:

• High fever
• Jaundice
• Bleeding through mouth, nose, eyes and/or stomach
• Kidney failure
• Liver failure
• Death

3.     Why is YF health problem in the world?

More than 90% of YF cases occur in Africa in 33 countries which are located in a band 15⁰N to 10⁰S of the equator, where an estimated 508 million people are at risk. In the Americas, YF is endemic in South America and several Caribbean Islands.

An estimated 200 000 cases and 30 000 deaths occur annually. However, fewer cases than these are reported. With increasing human encroachment into tropical forests, YF will remain a serious public health concern for some time.

4.     Is YF a serious health problem in South Africa?

YF does not occur in South Africa and travellers from endemic regions to South Africa should produce a YF certificate at the port of entry. The certificate becomes valid 10 days after vaccination and stays valid for 10 years. Failure to produce a certificate will result in the individual being kept under observation for 6 days, or being vaccinated against YF. The cost for either measure will be borne by the individual.

• Travellers to a YF endemic country
• People who live in countries in the tropical regions of Africa and South America.

YF is transmitted when an infected mosquito bites a susceptible person.

Early symptoms of YF are like those of malaria, typhoid fever and hepatitis. Any person who develops jaundice 6 days after the onset of fever should be considered a possible YF case. Diagnosis of YF can be confirmed by laboratory testing of blood samples.

8.     What is the treatment following YF infection?

There is no specific treatment for YF. Treatment is symptomatic and supportive measures are used. Dehydration and fever can be treated with oral rehydration salts and medication. Any secondary bacterial infection should be treated with specific antibiotics. Intensive supportive care may improve the outcome of seriously ill patients.

9.     How is YF prevented?

Vaccination with a highly effective and safe YF vaccine is the best way to prevent YF.
 
10.    Who should get the YF vaccine?

• Travellers to a YF endemic region
• People who work in tropical rain forests of Africa and South America
• People who live in tropical regions of Africa and South America.

11.    How and when is the YF vaccine given?

• In countries where it forms part of routine childhood vaccination, YF vaccine is given by injection to the upper right arm to babies at 9 months of age together with the measles vaccine.
• For all other candidates, one dose of YF is injected to the right arm.

YF vaccine is safe to administer to asymptomatic HIV-infected individuals. Individuals who have symptomatic HIV-infection should not be vaccinated with YF vaccine.

The YF vaccine is very safe. The most common side-effects are soreness at injection site, fever and headache. Severe reactions to YF vaccine are rare. Vaccination is contraindicated during pregnancy, except during epidemics when the risk of YFV transmission may be very high. The vaccine is contraindicated in children under 6 months of age and is not recommended for those aged 6 to 8 months, except during epidemics when the risk of YFV transmission may be very high.