In the future, more than 600 million people could be threatened by the dangerous Lassavirus. Over the next 50 years, changes in the climate and land use will significantly increase the region in which people can infect themselves with the often fatal hemorrhagic fever, reports a team led by Raphaëlle Klitting from the SCRIPPS Research Institute. As the working group writes in its publication in "Nature Communications", the Natal-Vertizzenmaus (Mastomy's Natalensis), a carrier of the Lassavirus, only bears the pathogen in a tiny part of its distribution area. According to the model of the working group, this area will increase dramatically by 2070. Instead of only previously in West Africa, Lassafieber could also spread in Central and East Africa.
The Natal multi-teat mouse is a cultural follower and seeks human closeness. She most likely transmits the virus via her droppings. However, while the vector occurs in almost all of sub-Saharan Africa, Lassa fever is only found in a few small areas in West Africa. According to Klitting's team, the reason for this is that certain environmental conditions are necessary for the virus to spread. For large areas of Africa, the virus is therefore too demanding.
Lassafieber is a serious and where it occurs, by no means rare illness. Of the several hundred thousand people who infect western Africa in Nigeria and other countries with lassafide, about 80 percent fall ill or symptomless. In the rest of the cases, however, a heavy hemorrhagic fever develops, which can go hand in hand with symptoms such as bleeding from the mouth and other body openings. Up to 80 percent of those affected die. There is no vaccination.
On this basis, the group modelled the ecological niche of the Lassavirus – with the result that temperature, precipitation and pasture land determine its distribution. As a second step, she combined this data with projections of future changes in climate and land use to determine the ecological niche of the virus in up to 50 years. In these projections, the range of the dangerous disease expands considerably.
Instead of just a few regions in West Africa, the possible distribution area of lassa fever in 2070 covers a wide belt from Guinea to Cameroon, with potential distribution islands in Uganda, the Democratic Republic of the Congo and on the coast of Mozambique. However, there is also good news. Using genetic analyses of lassaviruses from different regions, the team investigated their evolutionary dynamics. According to them, the virus spreads unusually slowly. It should therefore by no means be said that Lassa will really appear in all climatically suitable regions in the future, according to the conclusion of the group around Klitting. At least if the dynamics of the spread of the virus does not change unexpectedly.
