When Animals Make People Sick

Researchers estimate that more than two billion people a year get diseases spread by animals. More than two million of them die. 

Delia Grace is a veterinary epidemiologist — an expert in the spread of diseases involving animals. She is also a food safety expert. She works at the International Livestock Research Institute in Kenya’s capital, Nairobi. She says diseases transmitted between animals and people are called zoonoses. She says more than 60 percent of human diseases come from other vertebrate animals. Some of these diseases are common. Others are extremely rare.

Delia Grace says there are many different infection pathways for a person. Probably the most common one is for people to get sick from food. Other transmission pathways include direct contact with animals. And some diseases can be transmitted through water or through the air.Delia Grace says diseases like avian influenza or mad cow disease have killed very few people. But she says they are of interest because some of them could kill a lot of people. They include the Spanish flu after the First World War, and HIV, the virus that causes AIDS.

Delia Grace is the lead author of a new report called “Mapping of Poverty and Likely Zoonoses Hotspots.” She points out that poverty and disease are closely linked, so preventing the transmission of animal diseases could help reduce poverty.

The report, for Britain’s Department for International Development, lists places where the diseases are most common. The report lists places where a disease has existed for a long time, a so-called endemic zoonosis, as well as places with new threats. 

Delia Grace says things could get worse in the coming years as meat production increases to feed a growing world population. High production farms often raise animals close together. Crowding can allow diseases to spread quickly. Another concern is the use of antibiotics in food animals, not only to prevent and treat diseases but to increase growth. The report says an “incentive-based” system to encourage safer methods of raising animals could be more effective than increasing food inspections. For example, small farmers could receive training and other help that would lead to official approval of their products.