Zika virus: prevention and control

On 4 May, The International Association of Ecology and Health (IAEH) and Ecohealth Alliance hosted a Zika virus webinar. The speakers were Dr. Felipe Naveca, Deputy Director of research at FIOCRUZ ILMD Amazon institute in Manaus, and Dr. Jay Varma, Deputy Director of Infectious Disease at the New York City Department of Health. You should be able to get the recorded webinar from the Ecohealth website, if you’re interested, but I wanted to post a quick summary for you here.

What is Zika virus?

Zika virus is an arbovirus (arthropod borne virus) named after the Zika Forest where the virus was first documented. Zika virus isn’t new globally – it was first documented in 1947 – but it recently reached the Americas, where it has quickly spread. In Brazil, where other arboviruses are also highly prevalent, the incidence of Zika virus falls between that of Chikungunya and Dengue. Zika virus is particularly concerning because infected pregnant women are more likely to have spontaneous abortions and infants carried full term have a high risk of microcephaly.

How is Zika virus transmitted?

Zika virus is predominantly transmitted among humans by Aedes mosquitoes. However, it can also be sexually transmitted from an infected man to his sexual partners. (I don’t know if it can go the other direction.) Blood transfusions from infected individuals also lead to transmission.

How can individuals and governments control the spread of Zika virus?  

In countries/states/provinces that do not yet have a Zika epidemic, the best form of control is prevention and monitoring. The CDC recommends avoiding travel to regions with Zika virus and practicing strict mosquito avoidance (e.g., long sleeves, repellent) if you must travel to those areas. That’s especially important if you’re pregnant. Men traveling to Zika-infected areas should use condoms for months after returning to avoid transmitting Zika to their partners. Also, anyone traveling to infected areas should avoid denoting blood and avoid being bitten by mosquitoes after returning home. Infection can be asymptomatic (you don’t know you’re infected), so these precautions should be taken even if you don’t think you’re sick.

There is no vaccine for Zika virus, so the best ways to control the spread in epidemic areas are safe sex, mosquito avoidance, and vector control. There are many methods for vector control, and using a collection of methods will likely be more effective in the long run than using a single method (=a strong unidirectional selection pressure). Promising and effective methods include eliminating standing water where mosquitoes can breed, infecting mosquitoes with Wolbachia, selectively applying pesticides to reduce mosquito populations, and using female mosquitoes to spread pyriproxyfen among oviposition sites.

Could Zika virus establish in the Northeastern US?

At this point, it’s unclear. The CDC updated its potential distribution map for Aedes aegypti in the US to include regions much further north than the previous estimated distribution, but there aren’t necessarily any Aedes aegypti mosquitoes in those areas. There are other Aedes spp. mosquitoes in the Northeastern US, but at this point we don’t know if they would be competent Zika virus vectors or not. There’s also some question as to whether Culex mosquitoes can serve as vectors.

Does Zika virus infect any animals besides humans and mosquitoes?

Yes, Zika virus has been found in monkeys. But we still have very little information regarding zoonotic reservoirs for Zika virus.

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