Brazilian Cities in Danger of Yellow Fever Epidemic




razilian health workers are racing to vaccinate urban populations against the yellow fever virus in order to prevent a pandemic in its largest cities. In previous years, yellow fever has been confined to forest areas of the Amazon basin; if it spreads into city slums, the consequences to public health could be catastrophic.


The New York Times reports that “Brazil is suffering its worst outbreak of yellow fever in decades. The virus, which kills 3 percent to 8 percent of those who are infected, is now circling the megacities of Rio de Janeiro and São Paulo, threatening to become this country’s first full-blown urban epidemic since 1942.”


Yellow fever is a potentially deadly viral hemorrhagic disease transmitted by Aedes aegypti mosquitoes, which affects humans and other primates. WiRED International recently issued a medical and health education module on yellow fever. The module includes the infection’s description, its means of transmission, signs and symptoms, diagnosis, laboratory evaluation and treatment, as well as technical guidelines for health professionals.


Brazil’s Ministry of Health got off on the wrong foot when the outbreak started; it didn’t begin vaccinations, and it didn’t confront misinformation about the vaccine or how the virus is spread. Rumors circulated on social media that the vaccine was not safe. Misinformed people in Brazil began shooting and beating howler monkeys out of fear of yellow fever transmission, even though mosquitoes alone transmit the virus (see earlier story). A single dose of the vaccine normally provides lifelong protection, but the current goal of inoculating an urban population of 23 million presents a daunting task.


Brazil’s rainy season has begun, which means mosquitoes will breed and migrate in increasing numbers. WiRED will continue to report on the health crisis in that country. The key to containing any outbreak is for health professionals and general populations to be prepared and educated about disease health risks and prevention.



What Is Yellow Fever?

Yellow fever is an acute viral hemorrhagic disease, and, like Zika, it is transmitted to humans by infected Aedes aegypti mosquitoes. Yellow fever occurs in tropical and subtropical areas of Africa and the Americas. The “yellow” in the name refers to the jaundice that affects some patients. (Jaundice causes the skin and other body tissues to turn yellow.) The illness can range in severity from a fever to severe liver disease with bleeding. About 15% of people who get yellow fever become ill enough to experience bleeding, shock, organ failure and sometimes death.





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