Chemistry

Diseases caused by water (continued)


Yellow fever

THE yellow fever is an infectious disease caused by a flavivirus (the virus of yellow fever), for which a highly effective vaccine is available.

The disease is transmitted by mosquitoes and occurs exclusively in Central America, South America and Africa. In Brazil, the yellow fever is usually acquired when an unvaccinated person enters areas of transmission wild (cerrado regions, forests).

A person does not transmit yellow fever directly to another. For this to occur, the mosquito must bite an infected person and, after the virus has multiplied, bite an individual who has not yet had the disease and has not been vaccinated. It is also known as "black vomiting" because the vomiting of the infected person is dark due to internal bleeding (loss of blood).

The transmission of yellow fever in wilderness area is made through mosquitoes of the genus (mainly) Haemagogus. The virus cycle in wild areas they are maintained through monkey infection and transovarian transmission (mosquito passages to their offspring, children) in the mosquito itself.

Human infection occurs when a person unimmunized enters cerrado or forested areas. Once infected, the person may, upon return, serve as a source of infection for the Aëdes aegypti, which can then start broadcasting yellow fever in urban area.

A person may be a source of mosquito infection from immediately before symptoms appear until the fifth day of infection. O Aëdes aegypti becomes able to transmit the virus of yellow fever 9-12 days after biting an infected person. In Brazil, the transmission of yellow fever in urban areas It has not occurred since 1942.

In border areas of agricultural development, there may be adaptation of the wild transmitter to the new habitat and the consequent possibility of transmission of the yellow fever in rural areas ("intermediate").