Bird flu could join growing list of ills

ST. LOUIS – Humans risk being overrun by diseases from the animal world, according to researchers who have documented 38 illnesses that have made that jump over the past 25 years.

That’s not good news for the spread of bird flu, which experts fear could mutate and be transmitted easily among people.

There are 1,407 pathogens – viruses, bacteria, parasites, protozoa and fungi – that can infect humans, said Mark Woolhouse of the University of Edinburgh in Scotland. Of those, 58 percent come from animals. Most will never cause pandemics.

Experts fear bird flu could prove an exception. Recent advances in the worldwide march of the H5N1 strain have rekindled fears of a pandemic. The virus has spread across Asia into Europe and Africa.

Controlling bird flu will require renewed focus on animals, experts said at a news conference Sunday at the annual meeting of the American Association for the Advancement of Science.

Bird flu has killed at least 91 people since 2003, according to the World Health Organization. It appears to kill about half the people it infects. However, should it mutate so it can pass from human to human, it likely will grow far less deadly, said Dr. Stanley Lemon, of the University of Texas Medical Branch at Galveston.

Each year for the last 25 years, one or two new pathogens and multiple variations of existing threats have infected humans for the first time. Woolhouse told reporters it appears impossible the human species could endure such a rapid pace of new infections over thousands of years.

Woolhouse argues that either many of those diseases and other afflictions will not persist in humans or that there is something peculiar today allowing so many of them to take root in humans.

One explanation may be the recent and wide-scale changes in how people interact with the environment in a densely populated world that is growing warmer and in which travel is faster and move extensive, said Nina Marano, a veterinarian and public health expert with the National Center for Infectious Diseases. Those changes can ensure that pathogens no longer stay restricted to animals, she added.