Climate and spread of Viruses


Mosquito resting on green leafTerje Traavik has written a report on behalf on the Norwegian Environment Agency with the title: Climate Changes and emerging Wildlife-Borne Viruses in Norway: Facts, Uncertainty and Precaution.

The ongoing global climate changes will, with a high degree of probability, mean that Norwegian ecosystems and local communities are confronted with ”new” viruses that have reservoirs in, and are circulating between wildlife vertebrates and invertebrates. Our resident human, domestic animal and wildlife populations have little or no evolutionary experience with these ”new” viruses, and they may hence lack immunological protection against them. The viruses ”going north” include mosquito-borne viruses as West Nile Virus (WNV) and Dengue viruses (DENV); the tick-borne Tick-Borne Encephalitis virus (TBEV) and Crimean-Congo Hemorrhagic Fever virus (CCHFV); as well as rodent-borne hantaviruses and bat-borne rabies- and ebola-related viruses. Birds may carry viruses over wide distances within and between continents. The same is true for people travelling long distances while having virus in their blood (being viremic).

According to the international scientific literature scientists agree that the climatic changes represent strong drivers of the northwards virus invasions, although different authors may disagree on the relative impacts of climate changes compared to other anthropogenic changes to the environment and the various interactions between them.

Before “the virus invasions arrive”, a number of viruses are already circulating with small rodents, migrating birds, mosquitoes, ticks and midges as reservoirs and/or vectors, in the ecosystems of northwest Russia and Fennoscandia. The consequences of multiple viruses simultaneously infecting a common host- or vector-organism are unpredictable, and can only be clarified by targeted research.

Completely new virus strains may appear through different forms of exchange and recombination of hereditary material (DNA or RNA) between invading and resident viruses. Climate changes may enhance the frequency of such events. Furthermore, the invading viruses may be able to infect local host- and vector-species, and this may contribute to further increases in the number of virus mutants and hybrids. The biological characteristics of such viruses, including pathogenicity, are totally unpredictable.

In the present report, attention is focused on the ongoing virus invasions by:

– Explaining the complexity of the virus life cycles, and how these may be affected by climate change.

– Analyzing our capabilities to, on the basis of present knowledge, understand how the climate changes may affect the virus-host-environment interactions in the future.

– Outlining the areas of new knowledge necessary for design of more precautionary scenarios and models to predict the dimensions and consequences of the virus invasions.

– Recommending fast implementation of research, surveillance, monitoring and other initiatives that may make the society able to act precautionary in relation to the possible threats ecosystem-, domestic animal- and public health may become exposed to.

See the press release by the Norwegian Environment Agency here

Use this link if you want to read the report