GENEVA, Nov 17 (IPS) — The World Health Organisation’s new Division of Emerging Viral and Bacterial Disease Surveillance and Control (EMC) in Geneva is on stand-by to help with an outbreak of yellow fever in Liberia.

There have been 146 cases reported since July, 102 of which occurred in October with new cases still appearing. Final laboratory confirmation of the virus involved is still awaited but WHO officials say the symptoms which include jaundice and a high temperature, are all compatible with a diagnosis of yellow fever.

Symptoms include sudden onset of fever, headache, backache, muscle pains, nausea, vomiting, haemorrhaging, a slow and weak pulse rate and jaundice. The virus attacks the liver and the mortality rate may exceed 50 percent.

The disease, which can infect monkeys and some small mammals as well as man, is spread by the bite of Aedes mosquitoes and both the Aedes Africanus and Aedes Aegypti types have been found to be abundant and breeding rapidly in Liberia.

Yellow fever is endemic in the tropical zones of Africa and northern South America and ranked as one of the great plagues of the world during the last century with epidemics decimating populations and serious outbreaks occurring far from the endemic regions in Europe and the USA.

Thousands of workers died from it during construction of the Panama Canal. Discovery of how it was transmitted, however, led to mosquito control measures which reduced the incidence considerably and the last outbreak in the US was in 1905.

This and the subsequent development of a vaccine has reduced the number of reported cases are around 1,000 a year, although the true incidence is believed to be much greater.

‘’Yellow fever has been with us a long time,’’ says Dr. David Heymann, EMC Director in Geneva. ‘’It resurges when vector control is poor. It is hard to say whether it is increasing or we are just more aware of it.’’

One of the main problems, he points out is the worldwide break down in mosquito control activities. ‘’Aedes mosquitoes breed in small collections of water — in rolled up banana leaves or broken bottles. They are a growing problem with urbanisation, poor sanitation and refuse accumulation.’’ A bad rainy season can also boost the mosquito population.

‘’However we can protect against yellow fever — the vaccine is effective for up to 10 years,’’ he says. People can also contract the disease in a mild or sub-clinical form which also confers protection on them, sometimes giving life-long immunity.

‘’The problem in Liberia is that there have never been any recorded outbreaks before so none of the population is probably immune.’’ Kenya faced a similar problem with its first outbreak of yellow fever two years ago.

The vaccine can give protection within 10 days and so is useful in an epidemic situation. Some African countries have now begun to include yellow fever in their childhood immunisation programmes. Kenya did so after the outbreak in 1993.

However this is not without its difficulties in Africa, however, where AIDS is so widespread.

‘’This raised the whole issue of giving yellow fever vaccine to children who are HIV-positive,’’ says Heymann. WHO has been supporting research involving intensive surveillance of vaccinated children to ensure that there are no adverse reactions.

‘’We certainly recommend that no live vaccines, including yellow fever, are given to people who have developed the symptoms of Aids. The problem in Africa, though is that not many people are tested for HIV so we don’t know whether they are carrying the virus.’’

The vaccine is also not generally recommended for new born babies or pregnant women, although exceptions may be made in epidemic situations.

Vaccination has already begun in Liberia. ‘’This should bring it under control in a very short time and so prevent spread to other areas,’’ Heymann explains. The aim is to vaccinate the entire population of two million.

The recent civil war has caused large movements of population both within the country and to neighbouring states of Cote d’Ivoire, Guinea and Sierra Leone, which considerably increases the risk of spreading the disease throughout the region.

WHO has so far sent 100,000 doses of vaccine and medical equipment to Liberia and EMC remains ready to provide whatever further support may be necessary. (END/IPS/JMP/RJ/95)

Origin: Amsterdam/LIBERIA-HEALTH/ ----

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