"Infection: The usual suspects"

Read the full article in the Economist. (Subscription required.)

"Science has thus far counted 1,400 pathogens that affect humans. Mark Woolhouse and Sonya Gowtage-Sequeria from the University of Edinburgh have surveyed these and found that 13% are regarded as emerging (such as SARS or HIV) or re-emerging (such as tuberculosis, West Nile virus or malaria). Furthermore, the number of new pathogens emerging seems to be on the increase."

One or two new human pathogens are discovered each year. Some no doubt are discovered due to better surveillance. Some are transitory, to emerge and quickly disappear. But there may be changes in human ecology that promote the emergence of new diseases.

Most new diseases come from animals. As populations increase, and as more people live in close proximity to more livestock, there are more possibilities of transfer of diseases from livestock to man. Similarly, as agriculture extends ever further, more people are coming into more contact with more wildlife, and thus exposed to new animal pathogens. Moreover, more crowded conditions and more rapid transportation allows diseases that might once have infected a single person and never been diagnosed, to infect a group, spread and come to the attention of the public health officials.

"If many of the factors responsible for the emergence of new diseases—such as international travel, intensification of agriculture and urbanisation—are likely to continue, how is the world to respond to the threat of new diseases? The answer seems to be to spend more money on animal and human health, as well as on the monitoring and surveillance of pathogens. With the world an increasingly connected place, achieving high standards in these areas would be a global public good."

I would also recommend "Preparing for a Pandemic" (of Avian flu) by W. Wayt Gibbs and Christine Soares in the November 2005 edition of Scientific American.