Rainforest vs new diseases

Oct 1998

The destruction of the tropical rainforest is often accompanied by the outbreak of new unknown diseases. An unknown virus, for example, was discovered in the blood of the workmen who cut the road from Belém to Brasília through the jungle in 1950. Subsequently, 11,000 people fell ill with high fever and muscle pains. And the construction of the railtrack from Lima to La Oroya in Peru resulted in an outbreak of the so-called ‘Oroya fever’. The origin of the Aids virus, too, is thought to lie in the tropical rainforest.

The high biodiversity of the rainforest also promotes a high potential for unknown viruses – which can be set free by the ecological destabilisation of these areas. In Latin America, the extinction of big cats and the expansion of agriculture led to a massive increase of rodents, and hence of the Machupo virus. Other pandemics, like the Rift Valley fever, can be traced to the spreading of huge cattle herds and the explosion of mosquito populations that often accompanies clearfelling. ‘A change of host, for example from rodent to human,’ says virologist Kurt Roth of the Georg-Speyer-Haus, an Aids research institute in Frankfurt, ‘is favoured by a preceding mass increase of the virus population because the chances of successful mutations are growing too.’