20 Jan 2009

Yellow Fever

I don't know how many people pay attention to the news, but it is highly possible for a yellow fever outbreak soon in the future in Trinidad and Tobago.

Yellow fever is a serious viral infection, transmitted by mosquitoes in tropical regions. It has both an urban cycle and a jungle cycle that relies on monkeys as carriers ('sylvatic cycle').

In mild cases the symptoms are similar to influenza, but serious cases develop a high temperature and may have a series of after effects, such as internal bleeding, kidney failure and meningitis.

A classic feature of yellow fever is hepatitis, which is the reason for the yellow colouring of the skin (jaundice) and the name of the disease.

Yellow fever can cause sudden epidemics, with a mortality rate of almost 50 per cent. Although a safe, efficient vaccine has been available for the last 60 years, epidemics still occur, constituting a health risk in tropical regions.

The disease is covered by the International Quarantine Regulations, which are taken very seriously by authorities everywhere.

The virus is introduced into the bloodstream via the saliva of the mosquito as it bites.

The virus can then be transported around the body and reproduce itself in a variety of the body's cells, usually the liver, kidneys and blood vessels. In serious cases, these cells may become damaged themselves.

In addition, the cells of the immune system are affected and release large quantities of signalling substances. These substances are the cause of the normal disease symptoms, such as muscular pain and fever, which are also observed in influenza.

In its original jungle cycle, the mosquito sucks the blood of an infected monkey. The mosquito develops a permanent infection, in which the virus accumulates in its salivary glands. Then the mosquito bites another monkey, which then also becomes infected with the virus.

A person travelling through the jungle may also become infected by an infected mosquito. When this person returns to urban areas, a new cycle begins.

The incubation period from infection to developing yellow fever is 3 to 16 days.

Mortality ranges from 5 per cent to 40 per cent. Some people do not develop a serious form of the disease. They may have no symptoms at all or just a mild influenza-like illness.

In the actual full-blown disease there is:

    * high fever

    * generalised symptoms like violent headache, muscular pain, upset stomach and loss of fluid.

The fever dies down after three to four days and the general condition improves. However, in about 15 per cent of cases the fever returns within 24 hours and a dangerous situation develops.

And in terms of dengue, this is what the Express reported:

In addition to the six confirmed deaths, the report also indicated that out of the 8,534 reported dengue fever cases, only 333 were confirmed. On the other hand, while the ministry was only able to identify 3,832 of those reported cases, the Trinidad Public Health Lab only confirmed 100.

You got that? There were ONLY 333 confirmed dengue cases.