A CViSB study published in Nature Communications last week characterized the factors that support Lassa virus circulation in West Africa through analyzing environmental data associated with virus occurrence. The research team, led by postdoc Raphaëlle Klitting, utilized ecological niche modeling to pinpoint temperature, precipitation, and the presence of pastureland as key contributors to viral spread. Combining this analysis with projections of climate and population changes, the team determined that regions of Central and East Africa will likely become hospitable for Lassa virus over the next several decades, and that the population living in areas that are ecologically suitable for Lassa transmission may drastically increase by 2070.
Environmental factors may be of particular importance to understanding the spread of Lassa virus because the virus spreads in only some of the areas where the primary animal reservoir is present. Based on ecological niche modeling and land-use and climate projections, the research team estimated the current region of Lassa suitability, as well as the region in the years 2030, 2050, and 2070. While the current estimation greatly corresponded to areas where Lassa is already known to be endemic, the future estimations depict transmission well beyond West Africa.
“We found that several regions will likely become ecologically suitable for virus spread in Central Africa, including in Cameroon and the Democratic Republic of the Congo, and even in East Africa, in Uganda,” Klitting said.
When projected population growth in areas that are currently affected by Lassa is combined with the projected population growth in areas that may be affected in the future, the number of people exposed to Lassa is predicted to increase by more than 600% in fifty years. However, it is unlikely that the virus will spread into new areas very quickly. Phylogeographic analysis of viral genomes from different locations in West Africa suggests slow virus dispersal, meaning that without substantial changes in transmission dynamics, the spread of Lassa into new regions will be limited over the first decades.
The projected risk of expansion of the Lassa endemic area can and should inform critical public health policies, such as adding Lassa virus to lists of viruses under epidemiologic surveillance in parts of Central and East Africa. The research team also emphasizes that even without substantial expansion of Lassa in the immediate future, the need for more efficient prophylactic and therapeutic countermeasures is urgent due to viral circulation in increasingly populated endemic areas.
These findings were made possible through the interdisciplinary approach of CViSB-led research, specifically by combining molecular and evolutionary analyses with ecological and climate modeling. Read more.