When Outbreaks are in Season: Predicting High-Risk Periods for Transmission of Disease

Since the Ebola epidemic first struck in West Africa in 2014, much has been learned about the virus. However, a critical element to control this and other zoonoses, infections that pass between animals and humans, is the ability to predict when and where outbreaks will occur. Dr. Romain Garnier is on his way to Ghana to study an animal that harbors more diseases capable of making the jump to humans than any other mammal: bats. By looking at changes in the bats’ immune system over time, he hopes to discover important information about the circulation of viruses in the population. This might reveal a seasonal pattern of periods when more virus is present or when bats are less able to defend against the pathogens and, thus, an increased risk of spillover into humans.
Although it resembles other mammals’ in its basic elements, little is known about the bat immune system. Dr. Garnier is carrying out experiments and observations of a captive population of straw-coloured fruit bats known to carry the henipaviruses. This will allow him the unique possibility of following the same individuals over time and testing their immune responses, in particular, the production of antibodies, on a weekly basis. It is already known that female bats’ antibody levels change after giving birth, declining, rising, and dropping again. His first goal is to explain this pattern and track its impact on transmission of the virus. These fluctuations might indicate the mother bats becoming reinfected with henipavirus, or even that the virus is capable of lying dormant in bats until it is reactivated.
Secondly, Dr. Garnier will investigate the very important role of mother bats, as all mammals, in transferring antibodies to newborns. “It may prevent newborns from getting infected,” he explains, “and it could affect when the virus circulates most and, thus, the greatest risk periods for humans.” He will study this transfer, focusing on a phenomenon called allosuckling, where pups nurse from several mothers. This could change the dynamics of antibody transfer and infection. To determine if this is happening in the fruit bat colony, Dr. Garnier will use an innovative approach to monitor its effects by vaccinating females to stimulate antibody production and observing how they are passed to the young.
His ultimate goal is to construct mathematical models from all of this data in order to predict which time of year might pose more threat for the transmission of henipavirus to humans. If he identifies a risky season, researchers could then check if it exists in the wild. Models are extremely important tools for epidemiologists and Dr. Garnier believes his could be modified for other zoonoses representing a serious public health risk. Early response to outbreaks is crucial. If his predictions show a season of heightened risk, extra early response teams could be readied in advance of these periods, leaving us better prepared to face the next outbreak when it comes.

Scientific title : Dynamics of Antibodies Against Zoonotic Infections in African Fruit Bats

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