Zika conference highlights knowledge, but many questions remain
Woodruff Health Sciences Center | May 11, 2016
Female Aedes aegypti mosquito obtains a blood-meal from a human host.
Source: Public Health Image Library (PHIL), CDC
Scientists and public health leaders who gathered at the Emory Conference Center May 1-3 to focus on Zika virus disease agreed that while much work remains to be done in understanding and combating the disease, they are optimistic at the level of global collaboration, which so far has surpassed that of many other infectious disease outbreaks.
The "Bridging the Sciences: Zika Virus" conference was organized by the Global Virus Network (GVN) and Raymond Schinazi, PhD, DSc, director of Emory’s Laboratory of Molecular Pharmacology, with attendance by a number of scientists from Brazil as well as U.S. research centers. The GVN has launched a Zika task force led by Scott Weaver, PhD, scientific director of the Galveston National Laboratory in Texas, to connect researchers, coordinate exchange of scientific information worldwide, monitor the spread of Zika, and provide guidance to help prevent future outbreaks.
Three major areas of research and strategy emerged:
Mosquito control, geographic reach of the disease, and modes of transmission:
- Aedes aegypti mosquitos are believed to be the primary vector for Zika virus, particularly in Latin America. Other mosquitos such as Aedes albopictus may be involved in different areas of the world. Aedes aegypti contrast with other types of mosquitos, such as those that carry West Nile virus, in that Aedes aegypti are more indoor and adapted to densely populated urban environments.
- Researchers need to look ahead to conduct focused surveillance, identify the most likely next places of spread and study urban transmission chains. Public health educators should encourage targeted indoor spraying, installation of window screens, emptying water containers in yards, and wearing protective clothing.
- It won’t be possible to eradicate all the Zika-carrying mosquitos, so other strategies will be necessary and are being studied, including genetically modified or sterilized mosquitos that could replace current populations, and mosquitos treated with the bacterium Wolbachia to resist infection. Although there is convincing evidence that sexual transmission does occur separately from mosquitos, more information is needed about how long the infection can be transmitted through semen.
Development of therapeutics, and vaccines
- From Emory, several researchers reported on ongoing efforts in this area. Bryan Cox, PhD, from Schinazi’s laboratory, and Gaofei Lu, PhD, from the Emory Institute for Drug Development -- detailed drug discovery avenues. Christina Gavegnano, PhD, also with Schinazi's laboratory, and Mehul Suthar, PhD from Emory Vaccine Center focused on placental cells and immune cells that may influence transmission of Zika to fetuses. Suthar described a striking variation in infectivity of immune cells from human donors.
- Researchers are discussing both potential treatments for infected people as well as prophylactic drugs or vaccines, which could be given to a broader spectrum of the population at risk. Antibodies that are active against Zika virus infection are under development and could likely be available more quickly than vaccines. Vaccines are needed for widespread prevention and promotion of herd immunity, but highly effective vaccines will take many years to develop. Partially effective vaccines could help control the outbreak in the meantime.
- Researchers are proposing to repurpose drugs that have been effective against other insect-borne infectious diseases such as malaria, with potential combinations of drugs used to promote maximum effectiveness for both prophylaxis and treatment following infection. In addition, new drugs to treat Zika virus infection are being investigated. Because Zika is similar genetically to both dengue and West Nile virus and proteins from those viruses have been studied in molecular detail, researchers have several starting points.
Prevention of microcephaly and other birth defects:
- Pregnant women infected with Zika are at serious risk of transmitting the infection to their unborn children, who may be born with microcephaly or other birth defects, or may be miscarried or stillborn. Women should discuss risks, options, and preventive strategies with their physicians. Some studies in Brazil have used the rough rubric of testing all pregnant women with a skin rash. Better diagnostic tests are needed to detect Zika infection in fetuses, so that women need not live with uncertainty about the health of their babies throughout their pregnancies.
- Brazilian researchers have reported a concentration of microcephaly cases in the Northeastern region of the country around Recife. The reasons for this are under investigation, as well as the range of other potential defects, such as those affecting eye development.
- Distinct from the risk to developing fetuses, Zika infection is linked to Guillain-Barre syndrome in adults. It is unclear whether the neurological disorder is caused by infection or by a later auto-immune reaction.
- Zika virus appears to confer immunity to subsequent infection, contrasting with the interactions between the four dengue viral strains. So eventually researchers hope a substantial portion of the population in highly affected areas could be immune to Zika.
- Antibody-based therapeutics and vaccines currently under development should be fast-tracked and approved rapidly, scientists said. Even though these preventive therapeutics and vaccines may be only partially effective initially, they should be approved as rapidly as possible for use early in pregnancy and in girls and women of childbearing age.
Conference speakers were in agreement that government funding of research in Brazil, the United States, and other countries is urgently needed, along with continued international collaboration to combat the spread and impact of Zika virus disease.
The scientific conference was followed by a press briefing attended by reporters from NBC News, USA Today, National Geographic, the Associated Press, the Wall Street Journal, and Georgia Health News.