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BSI response to paper in Nature on Zika virus infection damaging testes in mice

A paper published today in the journal Nature has reported that male mice infected with a mouse-adapted strain of Zika virus can experience tissue injury associated with decreased testis size and reduced levels of two sex hormones and of sperm cells in the seminal fluid.  In response to this report, the BSI has issued the following statement:
Dr Peter Barlow, British Society for Immunology spokesperson and Reader in Immunology & Infection at Edinburgh Napier University said: 
“In humans, Zika virus has been shown to be present in the semen of males for many months after symptoms appear, but the direct effects of the virus on the male reproductive tract are largely unknown. This study used mice to look at how Zika virus could infect, and survive, in the testes over time.  This is particularly important as Zika virus can be sexually transmitted between humans, although such transmission is currently thought to be rare.  
“The study showed that one strain of Zika virus, which could efficiently infect mice, caused a decrease in the size and weight of the testes in mice, and caused damage to parts of the testes that produce semen. Zika also altered the levels of hormones that influence the production of sperm.  All of these effects translated to much lower rates of pregnancy when the male mice that had been infected with Zika were mated with females.  However, it is worth noting that when another strain of Zika virus was compared, one that did not replicate well in mice, the damage to the testes was not as serious. It is not currently known if all strains of Zika virus would have the same effects. 
“While it is currently unclear if Zika virus infection would cause reduced testes size and fertility in man, this study does raise concerns that Zika virus could potentially have direct effects on male fertility. Therefore, more work is needed to determine if these observations in mice would translate to men.”
The full paper that this comment is in response to can be found at: Govero et al.
Nature doi: 10.1038/nature20556