Zika: An Increasingly Frustrating Unknown Unknown

The last few days in Zika-land have been quite calamitous. Major changes in how the disease is conceived occurred. The first revolves around the sexual transmission of the virus from female to male. While male to female and male to male transmission had been known to take place for some time, female to male transmission was not really thought to occur though the virus has been found in the female genital tract and prolonged maternal viremia has been noted. This case, which occurred in NYC, illustrates that such transmission events are possible, though may be more rare than male to female transmission events. HIV, for example, is about half as likely to jump from female to male as it is from male to female.

The other big Zika news involves transmission of the virus in Utah from a fatal case to one of his caregivers. There is much to learn about this incident and it is difficult to hypothesize in such a context but several facts are known: the deceased had an extraordinary level of virus in his blood, the caregiver did not have sexual contact with the patient, mosquitoes in Utah are not known to harbor the virus, and the deceased was diagnosed with Zika post-mortem. 

This case, in my estimate, likely represents a chance transmission event that was facilitated by an extraordinary case of Zika in which the patient died (from Zika or from underlying illnesses) and possibly unique characteristics of the caregiver. It is unclear how generalizable this case may be but the mechanism as to how the caregiver was infected does carry important implications for the trajectory of the virus including the requisite infection control measures needed in the face of a virus that is present in multiple body fluids (blood, urine, semen, saliva).

Zika, more and more, is becoming an unknown unknown.