"With emerging viral diseases we just seem to be moving from emergency to emergency without a kind of sustained effort needed to maintain our capabilities, and to figure out a way to control vectors like Aedes aegypti, and Aedes albopictus." - Scott Weaver, PhD, FASTMH
Scott Weaver, PhD, FASTMH, a former ASTMH Councilor, is a leading expert on arboviruses—viruses transmitted by mosquitoes, ticks, or other arthropods. His research includes mechanisms of emergence from enzootic cycles, evolution, mosquito-virus interactions, and vaccine development.
Last year, you indicated that cases of Zika in Brazil might become a more widespread issue. What informed you that this was coming? I’ve been for a long time working on a group of arboviruses that have very similar histories of emerging from enzootic, forest transmission cycles in Africa and Asia and into an urban, human-mosquito-human cycle. Chikungunya, dengue and yellow fever viruses have a long history of doing this. Zika originated in the same kind of sylvatic mosquito-monkey cycles, so we suspected it had the same potential.
Last August when I spoke with you, the virus had been detected in Brazil for a few months, but the severe outcomes of congenital microcephaly and Guillain-Barré Syndrome hadn’t really been connected yet in Brazil.
Zika virus was first detected in humans in 1952, but we had not seen many cases of microcephaly and Guillain-Barré Syndrome being linked to Zika. Is the virus changing as it is moving to different populations?
There are a number of possibilities. One is that the virus did change recently in Asia. But it’s plausible that all Zika virus strains, everywhere they occur, have always had this potential, but we just never had a large number of cases in a short period of time where it got our attention.
You’re chairing the Zika task force for the Global Virus Network (GVN). What does that involve?
First of all, we will compile a database of membership expertise and unique resources that will be of use to the entire scientific community, as well as specific needs. We can harness the international representation of the GVN to help provide some of the resources that are needed to move along the research agenda and epidemiologic studies that are needed to understand Zika. Things like putting together banks of gold-standard Zika-immune sera are top priorities. Our other initial activity was to develop a frequently updated FAQ, which is now on the GVN website.
One of the big problems in the last few months is that it’s been hard to get virus strains out of Brazil because of export controls, so we’re trying to follow the virus’s spread into other areas of Latin America in order to obtain virus isolates that can be used for developing diagnostics, therapeutics, and vaccines.
[Editor’s note: Weaver says, “If you look at different organizations worldwide and where the expertise is on viruses like Zika, the American Committee on Arthropod-Borne Viruses (ACAV, a subgroup of ASTMH) would be way at the top of the list. Almost everybody I know in the U.S. who has worked on Zika is a member of ACAV.”]
Are you doing any fieldwork around Zika virus?
I was in Brazil from the 22nd to the 29th of February as part of the project on the epidemiology of Zika involving FIOCRUZ (Oswaldo Cruz Foundation) and Yale University’s Dr. Albert Ko. They have had a long-standing program on leptospirosis there. Basically, two other virologists at UTMB, Nikos Vasilakis and Shannan Rossi, and I are working with Albert to provide the virology expertise he needs to extend his project into arboviruses like chikungunya and Zika.
I was mainly involved in doing mosquito collections to try to get a handle of what populations of Aedes mosquitos are present in different neighborhoods in the city of Salvador. And now we’re doing experimental infections with mosquitoes that we collected in Brazil.
What was it like in the city of Salvador when you were out there collecting?
Everybody there knows about Zika. There’s been a huge amount of media attention there as you would expect. There have probably been more attempts at mosquito control than at any time in the past.
It’s very tough to gauge the situation with Zika because there’s a huge challenge with diagnostics in dengue-endemic areas, so you can’t just go out and sample people and see if they have Zika antibodies. If they’ve had dengue or even yellow fever vaccination, their immunity from those will cross-react with Zika. So if you can’t diagnose people in the early stage of acute illness, it’s very hard to diagnose them retrospectively in places like Brazil, and that makes it hard to know how many people have already been infected, how many people are still susceptible, and whether we’ll see another spike of epidemic activity this year, or whether perhaps the worst is over in places like Salvador.
Are you taking any specific laboratory precautions when working with Zika?
An issue that’s starting to get discussed a lot nationally is whether the recommended biosafety level for Zika—which was developed decades ago based on almost nothing being known about it, no history of recent lab infections or serious life-threatening diseases—is still appropriate. It’s a biosafety Level 2 virus, but we’re working with a few extra precautions here because the risk now is pretty certain to be much higher for certain groups of people.
What are the extra precautions that you’re taking with certain staff?
When we’re working with large cultures of Zika virus, especially when we’re doing centrifugation where there’s a risk of creating an aerosol, we’re putting warning signs on the doors and advising everyone to wear respirators. For animal research involving needles or other risks of being bitten, we have extensive safety discussions with persons who could be at high risk.
What more needs to be done on the funding front to figure this virus out?
There certainly is a need for more NIH funding to develop vaccines, therapeutics and better diagnostics. One general problem is that hardly anyone is doing arbovirus surveillance these days. There’s a very limited expertise of people able to go out and do field studies needed to understand the transmission of Zika and other arboviruses.
I keep thinking back to when West Nile virus arrived in the U.S. There was a consensus that we didn’t even have enough entomologists who could identify mosquitoes to do the kind of surveillance that was needed.
The CDC funded a few training programs for vector biology students including one here at UTMB, but funding dried ended several years ago. With emerging viral diseases we just seem to be moving from emergency to emergency without a kind of sustained effort needed to maintain our capabilities, and to figure out a way to control vectors like Aedes aegypti, and Aedes albopictus. Hopefully this Zika outbreak is getting so much attention that we can move to more stable research efforts going forward.
Do you have any sense of what might happen with Zika in the coming months?
The rainy reason will be coming in two to three months in Central America and the Caribbean. Transmission is likely to pick up there, or we’re likely to see a lot more imported cases into the U.S. At that point, with later spring and summer temperatures, and with Aedes aegypti all over the Southern U.S, there’s a risk from every one of those imported cases. Most of them will not lead to local transmission, but our experience with dengue and chikungunya tells us that some of them probably will.
We’ve had dengue outbreaks involving thousands of people. I think what would be different with Zika is if we have local circulation in the U.S., even if it’s only a few cases, there will be panic among those who live in those regions when there’s no way to completely eliminate the risk of pregnant women becoming infected.
What role can advocacy play in getting researching funding?
I think there are a lot of members of Congress who, if they have Zika cases in their local district, will recognize the need to increase and stabilize funding for arbovirus research. But hopefully some of them will be convinced even before that happens. We’ve gone through a period of a decline in constant dollars during the last 6-8 years in the NIH budget, and this a major problem. The stability of funding is very important to attract the best young minds into scientific careers.
We know that there’s going to be something else. Do you have any sense of what the next Zika is going to be?
There are some obscure flaviviruses in Africa, closely-related to Zika, that we know virtually nothing about. There are also some viruses that we know more about that could end up in the U.S. at any time, like Japanese encephalitis and Rift Valley fever, and there are undoubtedly many viruses out there that we haven’t even discovered yet that may have also this emergence potential.