Yellow fever has broken out in the jungles outside Brazil’s most densely-populated cities, raising a frightening but still remote possibility: an epidemic that could decimate that country’s population and spread throughout the Americas, including the United States.In an essay rushed into print by the New England Journal of Medicine on Wednesday, two doctors from the National Institutes of Health warn that cases of yellow fever, which can kill as many as 10% of those infected, have seen an unusual spike in the last few weeks in several rural areas of Brazil.
Those outbreaks have been limited to places where there aren’t enough people or virus-spreading mosquitoes to fuel a rapid run-up in transmission. But they are on the edge of major urban areas where residents are largely unvaccinated, and where both humans and insects are packed densely enough to accelerate the disease’s spread.
It’s a perilous moment, made more so by the fact that, while an effective vaccine against yellow fever has been around since 1937, worldwide stockpiles are all but depleted. In a series of yellow fever outbreaks in Angola and Democratic Republic of Congo two years ago, public health officials ran so short of the vaccine that they resorted to giving each person one-fifth of a dose.
Only a few companies worldwide manufacture the vaccine, and making additional doses takes a long time, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases and coauthor of the new essay.
In the virtual absence of stockpiled vaccine, wrote Fauci and Dr. Catharine I. Paules, “early identification of cases and rapid implementation of public health management and prevention strategies, such as mosquito control and appropriate vaccination, are critical” to preventing an explosion of yellow fever.
In an interview, Fauci said he considered it “unlikely” that an outbreak that has been confined to Brazil’s forest communities would spread to that country’s cities and catch fire.
With more than 1,000 suspected cases in Brazil and 371 confirmed by blood tests, “it’s not critical yet in Brazil,” he said. But he would worry, he added, if cases of yellow fever begin to turn up in such cities as Sao Paolo, Rio de Janeiro or Brazilia among people who have not come in from the jungles.
Fauci said it was important that his office “puts it on the radar screens” of both public health authorities and physicians. Most doctors have never seen yellow fever, which made its most frightening mark in the United States in Philadelphia in the fall of 1793. Brought in by people fleeing an epidemic in the Caribbean, yellow fever swept through the city, killing roughly 1 in 10 inhabitants.
Yellow fever is spread by the Aedes aegypti mosquito, which circulates in parts of the southern United States. But for yellow fever to gain a foothold in this country, many of those mosquitoes would need to feast on the blood of people who had been infected elsewhere and traveled here. Then, the mosquitoes would have to quickly move on to transmit the virus to others nearby. That chain of events would require a density of mosquitoes, infected travelers and innocent bystanders that, while possible, is improbable.
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SOURCE: Melissa Healy
Los Angeles Times
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