A woman stands near a poster to explain about the Zika virus, the Health Ministry office in Jakarta
(Copyright Reuters 2016)
CHICAGO – the Adult women in Puerto Rico were significantly more likely to develop Zika than men, researchers said on Thursday, raising new questions about the possible role of sexual transmission of the virus from males to females.
The study, published in the U.S. Centers for Disease Control and Prevention’s weekly report on death and disease, evaluated more than 29,000 laboratory-confirmed cases of Zika since the outbreak began in Puerto Rico in November 2015.
The data show that of all Zika cases with laboratory evidence of infection, 62 percent are female. The results pattern similar observations from Brazil, El Salvador, the authors say.
An obvious explanation could be that pregnant women are more likely than men to seek treatment for Zika because of the potential risk of birth defects.
To account for that, the researchers excluded all pregnant women who tested positive for the virus. Of the remaining 28,219 non-pregnant women and men who test positive for Zika, 61 percent of these cases occurred in women over the age of 20 years.
The Zika findings differ from earlier outbreaks in Puerto Rico of arboviruses transmitted by the same mosquitoes as Zika. For example, in 2010, the dengue outbreak and the 2014 chikungunya outbreak, infections were equally divided between men and women.
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“It is possible that male-to-female sexual transmission is a factor for this distortion of the burden of disease in the direction of the women,” the CDC said in a statement summary of the findings.
However, the contribution of sexual transmission to the general Zika rates is just beginning to be investigated, the CDC said. It could be that women are more likely than men to seek help when they are ill, or that women are more likely to develop Zika symptoms if they become infected.
The CDC is conducting tests on the blood of people who were in the vicinity of people with confirmed Zika to try to answer some of these questions.
Zika infections in pregnant women have shown that microcephaly – a severe congenital anomaly in the head and brain of small – and other abnormalities in the brain. The connection between Zika and microcephaly first came to light last year in Brazil, which has now confirmed that more than 2,000 cases of microcephaly.