Zika, dengue, yellow fever. All these ‘flaviviruses’ have threatened global epidemics in recent years, with outbreaks often emerging seemingly at random in different corners of the world. But prevention is always better than cure, and researchers at University of California, Davis (UC Davis) aspire to halt future flare-ups before they can reach the strength where they become a threat. They are starting with the birds and mammals that can carry such viruses.
‘We developed a machine-learning model that can predict potential unobserved wildlife hosts of flaviviruses,’ explains Pranav Pandit, from the One Health Institute at UC Davis. The model works by analysing data on species known to sometimes play host to flaviviruses, identifying common characteristics, and then comparing them with a database of 10,424 bird and 5,536 mammal species, to find wildlife with similar traits that therefore might be equally likely to act as hosts.
For example, of the 173 species identified as possibly playing host to the dengue fever, 139 had not previously been considered as potential carriers. By highlighting regions with a high diversity of species that should be newly prioritised in the global surveillance of flaviviruses, they have enabled the creation of maps highlighting the hotspots where new flavivirus outbreaks are most likely to emerge.
‘For instance, in South Asia, models identified three primate species with a high likelihood of being hosts for ZIKV [the Zika virus],’ explains Pandit. ‘At the time of data collection for this study, there were no outbreaks of Zika in South Asia. But, very recently there has been an outbreak in humans in India, indicating the need to strengthen wildlife surveillance for flaviviruses in these regions.’
This focus on a potentially major Zika outbreak in South Asia (which has not yet occurred but could do in the future) was one of the key findings from this model, along with the possibility of an outbreak of the Japanese encephalitis virus in Europe, due to the high density of potential host bird species on the continent.
This was published in the March 2019 edition of Geographical magazine
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