Mapping where new diseases come from: Zoonotics | 

Many, if not most, infectious diseases that afflict humans start out as animal diseases. That’s what the field of zoonotics is about — and why so many human disease experts worry about a flu that afflicts mostly birds (H5N1, aka avian influenza).

A mysterious killer of children in Cambodia is big news at the moment and it may well be a zoonotic disease.

A new study that mapped zoonotic hotspots reports one general finding that may challenge common wisdom — the finding that India and parts of Africa are responsible for most of the global animal-human disease transfer phenomenon.

News reports and expert commentary tend to focus on Asia, China especially, as central station for infectious disease (which does appear to be the case for bird flu anyway). This report may alter perspectives.

As this one map from the report showing poultry density indicates, India is actually a much bigger contributor to zoonotic disease:


Global poultry density

Other countries in sub-Saharan Africa like Ethiopia, Nigeria and Tanzania are also major zoonotic hotspots. As Reuters reports, this is an increasing problem that is not limited to poor or middle-income countries:

A global study mapping human diseases that come from animals like tuberculosis, AIDS, bird flu or Rift Valley fever has found that just 13 such diseases are responsible for 2.4 billion cases of human illness and 2.2 million deaths a year…. It also found the United States and Europe – especially Britain – Brazil and parts of Southeast Asia may be becoming hotspots of “emerging zoonoses”, which are infecting humans for the first time, are especially virulent or are becoming drug resistant.


Farm animals and global health | 

Flickr, Maurice

Miss Piggy

The Guardian has a good report today on the very important, but often neglected, connection between livestock in agriculture and human health.

Scientists call it zoonosis, but you can think of it as where HIV, cholera, avian flu, plague and many other (in fact, most) human diseases come from.

Though this natural evolutionary tendency for infectious bugs to move from infecting animals to humans (and vise versa) often happens in the wild, many experts think poor agricultural hygiene methods used in the developing world means it is happening with greater frequency on farms.

Says The Guardian:

A new human disease emerges around every four months, usually after jumping from animals. Many of these infections are minor and of interest only to microbiologists. But as intensive agricultural production expands and populations push into uninhabited areas, epidemics of devastating diseases, like Sars and HIV, which started out as animal pathogens, are likely to become more common.