The Washington Post reports on the view of many infectious disease experts that the rate at which pathogens are jumping from other species into humans is increasing.
"Influenza is a zoonotic disease. HIV is a zoonotic disease. Monkeypox. SARS," said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. "You can go on and on."
The increasing pace is being caused by a confluence of factors that bring people into contact with a greater diversity of creatures than ever before, experts say.
Many reasons are cited for this. There are more humans. Humans are pushing into more parts of the globe. There are farming and marketing practices (e.g. the live animal markets in South China) that increase the chance of contact between humans and other species. When a disease does jump into a single human its odds of spreading into other humans is increased by faster and more widely used modern transportation. Contaminated food is spread more widely by modern transportation as well. Humans keep and trade in exotic pets.
The article mentions in passing that smallpox may have originally jumped into humans from camels. There is an interesting story behind that. Camelpox has been found to be genetically closest to human smallpox of all the known pox viruses. There is a real possibility that camelpox could mutate in a way that would allow it to jump into humans.
All the comparisons showed that camelpox and smallpox are genetically closer to each other than to any other virus. The authors speculate that the two viruses evolved from a common ancestor, possibly a rodent virus, probably after the advent of intensive agriculture about 7,000 years ago.
Gubser and Smith say the growth in the percentage of people who are "immunologically naïve" for orthopoxviruses increases the danger that these viruses will emerge or re-emerge as a threat to human health. In addition, the growth in the number of people whose immunity is suppressed by HIV infection poses a risk that the orthopoxviruses such as camelpox will jump species and adapt to humans.
There is a new theory just published about the origins of HIV. HIV may have been created by an exchange of genetic material between two Simian Immunodeficiency Viruses (SIVs).
A genetic study of SIV - the Aids-like virus that infects monkeys - suggests that HIV - the virus that causes Aids in humans - came about through the combination of two viruses in chimpanzees.
In some ways, SIVcpz was found to resemble SIVrcm, a virus endemic in red-capped mangabeys.
But in other respects it closely matched another form of the virus, SIVgsn, which is found in the spot-nosed monkey.
"The genetics does not tell you how it arose," he said. "If you ask me to put money on it I think SIVcpz arose when monkeys and chimps were kept together in captivity. We know Asian rhesus monkeys caught SIV from African monkeys in captivity."
If this theory becomes well known and achieves some degree of acceptance one could easily imagine animal rights activists citing it as an argument against zoos.
|Share |||Randall Parker, 2003 June 15 12:56 PM Dangers Natural Bio|