Infectious Diseases Outlook for 2016: John Bartlett's Predictions

John G. Bartlett, MD


May 10, 2016

Zika Virus Epidemic

The most important infectious diseases (ID) story for early 2016 is the exploding epidemic of Zika, with widespread penetration in Central and South America, Mexico, and the Caribbean. The epidemic has had substantial consequences in Brazil, where more than 1.5 million cases of Zika infection have occurred. As of April 23, 2016, the Brazil Ministry of Health reported 7228 suspected cases of microcephaly or other nervous system malformation in newborns, with 1198 confirmed cases of Zika-related microcephaly.[1] Extraordinary features of the virus are sexual transmission by infected men and its devastating neurologic complications, including microcephaly, meningoencephalitis, and Guillain-Barré syndrome.[2,3,4]

The ID world is rife with a history of explosive, unanticipated epidemics. Since 1980, the tally includes the following:

None of these epidemics were expected, and nearly all had a profound impact on the healthcare system.

The global consequences of Ebola virus were substantial, and the ID world was caught embarrassingly off guard. This prompted Bill Gates to write an editorial in the New England Journal of Medicine[5] calling attention to our slow response and the need to be ready for the next epidemic.

Zika virus was a turning point. The ID and public health response was rapid and extensive—led by the Centers for Disease Control and Prevention (CDC), with frequently updated guidance documents, development of three Zika diagnostic tests, careful epidemiologic studies, and detailed predictive monitoring. By April 11, 2016, the National Library of Medicine had indexed more than 500 Zika-related articles, the CDC had published more than 10 guidance documents,[6,7,8,9,10,11,12,13,14,15] and New York City had a 6-point Zika plan. The National Institutes of Health Vaccine Research Center and several private companies are actively working on Zika vaccines.

A major question is whether Zika virus will reach the United States, not only from infected travelers but also from indigenous mosquitos. To date (April 27, 2016), 426 cases of Zika virus infection have been acquired by US citizens who traveled to countries where Zika is endemic.[16] This includes 36 pregnant women, complicated by one case of microcephaly and one case of Guillain-Barré syndrome. So far, eight sexually transmitted cases of Zika virus infection have been reported in the United States, all in men who recently traveled to "Zika zones." No known mosquito-transmitted cases in the United States have yet occurred.[16]

Another key question is where the Zika virus epidemic may come to the United States. This issue was addressed by an extraordinarily comprehensive National Institutes of Health/National Aeronautics and Space Administration-sponsored review that analyzed geographic variations in temperature, rainfall, travel patterns, poverty, prevalence of mosquito-transmitted diseases, and air traffic patterns in countries with a high burden of Zika.[17] Endemic transmission in the United States is most likely to occur in cities in south Florida and south Texas. The probability of Zika virus transmission declines across the United States from east to west and from south to north, but the entire eastern seaboard to New York City appears to be vulnerable. Contemporary planning resembles the recommendations for preventing West Nile Virus, an earlier epidemic virus transmitted by the Aedes aegypti mosquito.

Major ID outbreaks will continue to occur, but the "what and where" of these epidemics will defy our existing technology.


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