Can Zika virus asymptomatic host (carrier) enhance Zika transmission and spread?
Hi Ernest,
That is a difficult question to answer. The simple answer is that any infection that promotes viraemia will increase the probability of onward transmission as it provides a possibility for infection of mosquitoes which in turn can transmit to others thereby maintain the enzootic cycle.
The full answer is that we do not know the level of viraemia in asymptomatic infections for animals or humans. We do know that viraemia in clinical cases is extremely transient so asymptocatic human infections may not play a major role. However, given the sheer number of infections it is reasonable to assume that this at least contributes to continued transmission.
I expect that the natural reservoir / amplifying host plays a critical role in tranmission and spread; however, we only have hypotheses regarding which species acts as these hosts so firm conclusions cannot be drawn at present
If I had to bet, I would say that the answer for the spread, besides possible changes within the virus, relies on the asymptomatic host. But just to be clear here, no proof at all, being completely speculative.
Live stream from Senate Committee on Health, Education, Labor and Pensions Hearings re: growing Zika threat tomorrow 2/24/16 at 10AM United States EST might interest you. If so, here is the link:
http://www.help.senate.gov/hearings/zika-virus-addressing-the-growing-public-health-threat
Dear Ernest,
Most vector-borne viruses have different impacts on different infected individuals, even if the virus strain is the same in all hosts. In controlling spread, it is always advisable that those expressing symptoms and who have been diagnosed with the virus be isolated in areas where they are not exposed to competent vector mosquitoes, until their viremia has cleared. Naturally, asymptomatic individuals, or those who have not received clinical attention, may remain exposed to mosquitoes and thus may increase the dissemination of the virus. This is certainly the case with Zika, along with others such as dengue, Chikungunya, etc. What I've stated above applies to asymptomatic human hosts. The degree to which this virus is able to infect other hosts, thus circulating as a zoonotic agent, has not been well studied, especially outside its original home range in Central Africa. Nevertheless, given its transmission principally by Aedes aegypti and Aedes albopictus, which tend to be synanthropic and peridomestic, non-human reservoirs as epidemiological factors are not likely to be highly important to spread within human populations.
Below, I have attached some links to blogs with other information on Zika and other pathogens spread by Aedes mosquitoes.
Best wishes,
Bruce
https://www.linkedin.com/pulse/zika-dengue-yellow-fever-west-nile-viral-encephalitis-david-bruce?trk=pulse_spock-articles
https://www.linkedin.com/pulse/zika-just-one-character-diabolical-cast-david-bruce-conn?trk=pulse_spock-articles
https://www.linkedin.com/pulse/chikungunya-zika-emergence-predicted-years-ago-theres-conn?trk=pulse_spock-articles
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