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Model Sheds Light on Pattern of Dengue Virus Outbreaks

Both environmental and immunological factors play a role

WEDNESDAY, July 26 (HealthDay News) -- Cyclic multi-annual outbreaks of dengue virus, some lasting as long as nine years, are likely due to a combination of both seasonal fluctuations in vector demographics and a short-lived period when infected patients have cross-immunity to other dengue strains, according to a study published online July 25 in the Proceedings of the National Academy of Sciences.

Helen J. Wearing, Ph.D., and Pejman Rohani, Ph.D., from the University of Georgia in Athens, Ga., used theoretical modeling to understand how different hypotheses concerning dengue infection and transmission might explain these multi-annual cycles of disease outbreak.

Using data derived from dengue outbreaks in Thailand as a reference, the authors found that a four-month period (range is typically two to nine months) in which patients had cross-immunity to different dengue strains produced the expected multi-annual fluctuation, with strain variation and antibody-dependent enhancement (ADE) having minimal effects. ADE is a process where waning antibody levels produce a more potent subsequent infection by allowing the virus to replicate more efficiently. ADE alone produced fluctuations of 10 years or more.

"In addition to influencing interepidemic periods, accurate assessment of the roles of ADE, variation in serotype virulence, and temporary cross-immunity have important public health consequences, namely for infection persistence and eradication," the authors write. "Because of the importance of the pathogenesis of dengue hemorrhagic fever, any vaccine will be required to protect against all four serotypes."

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