Animal diseases that spread to humans are a growing global threat but for the moment, scientists cannot predict when or how they will occur, a U.N. expert said on Wednesday.
Known zoonoses, or diseases that can jump species, include bird flu which has swept parts of Asia, the Ebola virus that killed hundreds in Africa in the 1990s, and West Nile fever which is now well implanted in the United States.
One of the world’s most devastating diseases, HIV-AIDS, also was originally transmitted to humans by animals, though it now passes human to human without an animal link.
Problem likely to get worse
“One of the conclusions was that zoonotic diseases are increasingly emerging as a serious global and regional issue that is likely to grow in importance,” said Francois Meslin, the World Health Organization’s coordinator for control of zoonoses.
“But for the moment we have no way to predict when they will occur or under what circumstances,” he told reporters after a three-day conference on the problem.
Meslin heads a team set up a year ago by WHO, the U.N. Food and Agricultural Organization and the International Office of Epizooties to coordinate the global battle against zoonoses.
Zoonoses are often spread by international trade, not only in animals from tropical and sub-tropical regions but also in ordinary goods and produce on which viruses can hitch a ride.
Migration, environmental decline to blame
Meslin said the major factors leading to cross-species infections were environmental degradation in developing countries, particularly in tropical regions, and the movement of human rural populations into big cities.
But tropical countries were not always the source of zoonoses or zoonosis-like infections, as in the case of SARS and of Creuzfeld-Jakobs, popularly known as “mad cow disease,” which is believed to have first occurred in western Europe.
He said it was vital for governments to raise public awareness of the dangers and to ensure international and national trade in animals is properly supervised.
Meslin said the 60 experts attending the meeting discussed SARS, or severe acute respiratory syndrome, which killed nearly 800 people in an outbreak that began in China in late 2002 and was declared over last July.
But he said the disease, which has resurfaced on a small scale in Beijing over the last three months, had not yet been formally identified as a zoonosis since the link to civet cats some researchers have blamed for SARS has not been established.