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Zika Virus: An Emerging Health Threat

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Credit: Kraemer et al. eLife 2015;4:e08347

For decades, the mosquito-transmitted Zika virus was mainly seen in equatorial regions of Africa and Asia, where it caused a mild, flu-like illness and rash in some people. About 10 years ago, the picture began to expand with the appearance of Zika outbreaks in the Pacific islands. Then, last spring, Zika popped up in South America, where it has so far infected more than 1 million Brazilians and been tentatively linked to a steep increase in the number of babies born with microcephaly, a very serious condition characterized by a small head and brain [1]. And Zika’s disturbing march may not stop there.

In a new study in the journal The Lancet, infectious disease modelers calculate that Zika virus has the potential to spread across warmer and wetter parts of the Western Hemisphere as local mosquitoes pick up the virus from infected travelers and then spread the virus to other people [2]. The study suggests that Zika virus could eventually reach regions of the United States in which 60 percent of our population lives. This highlights the need for NIH and its partners in the public and private sectors to intensify research on Zika virus and to look for new ways to treat the disease and prevent its spread.


Climate and Viral Illness: El Niño Event Linked to Dengue Epidemics

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Dengue Incidence Score Video
Caption: Incidence of dengue fever across Southeast Asia, 1993-2010. Note increasing incidence (red) starting about June 1997, which corresponds to a period of higher temperatures driven by a strong El Niño. At the end of the El Niño event, in January 1999, dengue incidence is much lower (green). Credit: Wilbert Van Panhuis, University of Pittsburgh

Just as the severity of the winter flu fluctuates from year to year in the United States, dengue fever can rage through tropical and subtropical regions of the world during their annual rainy seasons, causing potentially life-threatening high fever, severe joint pain, and bleeding. Other years—for still unknown reasons—dengue fizzles out. While many nations monitor the incidence of dengue within their borders, their data aren’t always combined to track outbreaks across wider regions over longer times.

Now, NIH-funded researchers and colleagues, reporting in Proceedings of the National Academy of Sciences [1], have linked an intense dengue epidemic that struck eight Southeast Asian countries starting in mid-1997 to high temperatures driven by the strongest El Niño event in recent times. El Niño is a complex, irregularly occurring series of climate changes in the Pacific Ocean with a global impact on weather patterns. This new insight into climatic factors associated with dengue transmission could enable better prevention measures, which may soon be needed because climatologists are predicting another strong El Niño event next year due to unusually high ocean temperatures in the equatorial Pacific.