New study shows Zika infectious period ranges from 2 weeks to 3 months

There hasn’t been much in the news recently on the Zika virus. [Perhaps Trump is entertaining enough such that the news folks have enough news (fake or otherwise) to attract readers.] More likely it’s because the Zika virus is transmitted by mosquitoes which are largely dormant in the winter.

Chances are we have not heard the last about Zika.

Very little was known about Zika when infections were first being identified. Among the outstanding questions, how long does a person carry the virus once he/she is infected? The New England Journal of Medicine recently published a study addressing this.

First, it’s notable that the Zika infection looks a lot like the flu. See this table of symptoms (below, from the NEJM article):

To address the question of viral persistence, this study tracked men who had been infected and tested various body fluids at routine intervals to see when virus was no longer detectable. Not all people are the same, so the NEJM reported on the average clearance time (when half the people ceased having detectable virus) and the outer end of the time range (the time it took for 95% of men to clear the virus).

In blood, 50% of patients had no detectable virus in two weeks (14 days). However, the outlier patients took 54 days (almost two months) for their blood to be free of virus.

Notably, virus was detectable in semen longer, with 50% and 95% clearance times of 34 days and 81 days respectively.
Zika is still relatively uncommon in the U.S.:

  • 5,040 Zika virus disease cases reported in the U.S. to date.
  • Zika is epidemic in Puerto Rico, where 35,930 cases have been reported.

Aside from reading the latest scientific trials, the best source of information I’ve found is the CDC (Center of Disease Control) website. The site contains thorough, accurate, up-to-date information that is accessible and easy to understand. I highly recommend the CDC website as the go-to source for any questions that arise.

Sources: Persistence of Zika Virus in Body Fluids — Preliminary Report (NEJM)Center for Disease Control and Prevention

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