Will the latest coronovirus emergency become a worldwide pandemic? Will this be a repeat of the outbreak of Spanish Flu which killed tens of millions after World War1? Do you think it surprising that Science and modern medicine cannot anticipate and control such events?  Will it happen again? Of course!

Viruses and other pathogens regularly and inevitably evolve to overcome the immune systems of their hosts in order to survive. And sometimes their renewed ability to infect one species enables them to infect other hosts. Viruses which usually only infect one species such as chickens or bats can change to also infect humans. The chance of this happening is greatly increased if the usual host becomes in close contact with humans, as when wildlife are killed for food or made captive for other reasons. The Lyssavirus,  closely allied to the rabies virus, but which normally only infects fruit bats, for example, can cause severe infections in humans when wildlife rescuers rear orphaned or injured bats.

Viruses and other pathogens are spread more easily when the hosts are concentrated into a small space and the chance of transmission by contact or through aerosols, urine or faeces is increased. This is rare amongst wildlife species as the individual animals are well dispersed. A bat colony is an exception. But when large numbers of people live and work in close proximity in cities the opportunity for the spread of viruses is greatly increased. Large populations of people need reliable food supplies and these are provided by farms which rear and maintain food animals such as chickens and pigs in small areas. So the chance of an animal virus evolving to infect humans and the chance of that virus spreading rapidly through the population is greatly increased. A further aspect of the present epidemic is the possibility that the new virus came from wildlife which were being used for human food.

We humans are clever enough to devise ways to combat epidemics with vaccines and to treat those who are infected, but we seem incapable of changing our behaviour to avoid the risk of them happening in the first place.