Animal Diseases Pose Growing Threat to Humans

Only about 177 of these are considered to be emerging or re-emerging, but most are not expected to cause a pandemic. Currently, the H5N1 strain of avian flu is being very carefully watched for its pandemic potential, because it appears to be spreading around the globe. To date, about half of the humans infected with this strain have died. However, the victims are thought to have been infected by chickens or birds that had the flu, not by other humans.

The process of animal diseases jumping to humans has been going on for thousands of years, but over the past 25 years, it appears to be speeding up. Scientists are not certain why this is so. One hypothesis is that the earth is growing warmer and is more densely populated, while people are traveling faster and more frequently, thereby encouraging the crossover. Among the animal diseases that have made the crossover during this time are HIV, the Marburg virus, and severe acute respiratory syndrome (SARS).

According to Mr. Woolhouse, humans have always been attacked by novel pathogens. "The process has been going on for millennia. But it does seem to be happening very fast in these modern times.”




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