Dealing with another outbreak of yellow fever

With news of yellow fever outbreak in different parts of the country, Dr. Olayide A. Jinadu, Medical Director at Charis-Med Hospital, Lagos, sheds light on what the illness is about, what causes it and how to curtail it. GERALDINE AKUTU reports.

What is yellow fever?

Yellow fever is one of the acute viral haemorrhagic diseases (others being Ebola, Lassa fever, Marburg and Dengue) caused by a single-stranded RNA virus of the genus Flavivirus.

Yellow fever is characterised by jaundice (yellowness of the eyes), thereby necessitating the name “Yellow fever.”

It is a mosquito-borne disease, which means it is transmitted by mosquitos, and is endemic in tropical areas of Africa, Central and South America.

Yellow fever is transmitted specifically by the female Aedes aegypti mosquito. This particular mosquito also transmits Dengue fever, another acute viral haemorrhagic disease.

The key words in acute viral haemorrhagic diseases mean the following: Acute, which means sudden onset, within 24 hours.

The word acute has nothing to do with the severity of a disease as most people think, but the time of onset.

The opposite of Acute is Chronic, meaning prolonged duration of onset. Viral means caused by a virus, while Haemorrhagic means bleeding.

Some sources say Yellow fever was first diagnosed in Jos, Plateau State in 1953. It is also estimated that up to 100,000 cases of yellow fever may have occurred during the reported epidemic in 1969 in the same city of Jos, Plateau state.

The disease occurs when the female Aedes aegypti mosquito carrying the yellow fever virus feeds on a human being.

Epidemics occur when an infected person(s) introduce the virus into densely populated areas with high mosquito density and in places with low socio-economic status, where most people have little or no immunity, due to lack of vaccinations.

These areas also have poor drainage systems, which encourages breeding of these mosquitoes, allowing a very effective transmission from person to person.

It should be noted that not all cases of Yellow fever end up being severe.

In fact, it is estimated that only about 15 percent cases become severe, further implying that a minute portion of patients who contract the yellow fever virus develop severe symptoms and approximately half of the people with severe cases die within seven to 10 days.

Yellow fever, just like malaria, can be contracted via mosquitos, the difference here is that malaria is transmitted by the female Anopheles mosquito, while yellow fever by the female Aedes aegypti mosquito.

Why are these diseases transmitted by female mosquitos? It is because they need the iron and protein present in blood to make their eggs.

Secondly, malaria does not have a vaccine yet, while yellow fever disease does, and is able to provide effective immunity within 10 days for 80 to 100 percent of people vaccinated, and within 30 days for more than 99 percent of people vaccinated, according to World Health Organisation’s (WHO) data.

Healthcare workers are particularly susceptible to this dreadful disease, owing to repeated exposure from infected patients.

Therefore, health workers are mandated to receive a dose of the vaccine, if they have never been vaccinated against yellow fever. A booster dose is not necessary.

What are the signs and symptom? How is it diagnosed?

It cannot be overemphasised that yellow fever is usually a mild, self-limiting illness that would not need any specific treatment, consisting fever, headaches, myalgia (generalised body pain) and malaise (generalised body weakness).

Most severe yellow fever illnesses present with malaise, fever, chills, headaches, low back pain, nausea, dizziness.

This is followed by a period of remission, where the patient may either recover fully or progress to a more fatal form.

A return of the symptoms is usually marked by fever, vomiting, abdominal pain, renal failure, haemorrhage (bleeding from body orifices), jaundice (yellowness of the eyes), hepatomegaly (enlargement of the liver), mucosal bleeding, gastrointestinal bleeding, altered sensorium semi consciousness), tachycardia (increased heart rate), low body temperature or high grade fever and hypotension (low blood pressure).

Diagnoses are made from a series of such laboratory investigations as complete blood count (CBC), coagulation studies, blood electrolytes, urinalysis, chest X-ray to evaluate the level of pulmonary oedema and to reveal secondary bacterial chest infections, liver function test.

More specific tests are Rapid detection methods (polymerase chain reaction) and Serologic tests, among others.

What is the treatment for yellow fever?

No specific treatment exists for yellow fever as it is treated symptomatically.

This means symptoms that manifest are treated especially in critical cases. For instance, there are fluid resuscitation, antipyretics and fever management.

The current available vaccines confers near lifelong immunity of 95 percent of patients. Revaccination is recommended every 10 years for travel certificates.

How affordable and available is the vaccine?

The yellow fever vaccine is very readily available in most or all state hospitals and healthcentres at extremely subsidised rates.

Just walk into any of the nearby government owned health care facility and it would be made available to you. It is one of the vaccines mandated in the vaccination schedule for babies.

How can people reduce chances of getting infected with the virus?

The most important means is by getting vaccinated. Others are ensuring that safety precautions are taken at all times, ensuring suspicious cases are reported to appropriate quarters in time.

It is also important to wash hands regularly with soap and water, steering clear of individuals with such symptoms and ensuring the vectors (female Adedes aegypti mosquitos) are eradicated by clearing surrounding bushes and gutters or artificially made water bodies.