Putting thousands more people on antibiotics for anthrax is probably spawning a bigger threat than an anthrax superbug — more lethal everyday germs, doctors and researchers warn.

The long, 60-day treatment for anthrax gives other germs present in the body extra time to develop resistance to Cipro and other antibiotics, the experts say. They are worried because the same drugs given for anthrax are also taken for many other germ infections, sometimes as a last resort.

"For people who are on Cipro for ... 60 days, there's a good chance their normal bacteria will become resistant," said Philip Hanna, an anthrax researcher at the University of Michigan.

Such germs can cause sexually transmitted diseases, pneumonia, blood poisoning and other ailments. They are especially dangerous to people with weakened immune systems, such as AIDS or cancer patients on immune-suppressing drugs.

Antibiotics taken for anthrax come into contact with billions of other bacteria that routinely find a welcome home in the human body. Bacteria can grow new generations in minutes, so they can evolve drug resistance very quickly.

Many bacteria in the human body, unlike anthrax, are contagious when they cause a disease. Some are manageable at low levels but make people sick when they proliferate. Some become dangerous when people get sick with something else.

Worries about drug resistance are growing because it's now likely that more doctors might prescribe antibiotics simply for flu-like symptoms — just in case it's anthrax. On Wednesday, a New York woman died from the disease, though she had no known exposure at work.

Experts say if Cipro is taken for a few days while anthrax test results are awaited, that too can contribute to resistant bacteria. That routine can kill off the weaker common bacteria and let stronger ones flourish in the absence of competitors.

"If we have a lot of people taking a short course of Cipro, we have the classic situation of a lot of people developing antibiotic resistance," said Dr. Richard Corlin, president of the American Medical Association.

"There will be many more people affected by the antibiotic ... resistance effect than will be affected by anthrax," predicted Dr. Stuart Levy of the Tufts School of Medicine in Boston. Levy, a researcher in antibiotic resistance, is founder of the international professional group Alliance for the Prudent Use of Antibiotics.

Penicillin, the 20th century marvel discovered in a lowly mold, eventually lost its force against some staph infections from heavy use in the years after World War II. Later, it became weak against the venereal disease gonorrhea after many U.S. soldiers needed treatment upon return from Vietnam. In the early 1990s, dozens of Americans died in tuberculosis outbreaks around the country. Some of those germs were resistant to multiple antibiotics.

The anthrax outbreak has prompted antibiotic treatment for tens of thousands of people, largely with Cipro. Beyond that, 62,747 more Cipro prescriptions were sold by stores and through the mail in the third week of October alone than in the same week a year ago, according to the latest data from NDCHealth of Atlanta, a pharmaceutical tracking company.

Still, there are several reasons why anthrax itself probably won't develop quick resistance — at least from the current scale of antibiotic use — though the germ can be formulated intentionally as a drug-defeating weapon of war or bioterrorism, specialists say.

For one thing, anthrax has been a very rare disease over the past century, so the germ has barely faced antibiotics. Even now, the vast majority of people taking antibiotics for anthrax are presumably not infected. Even if someone did contract a resistant strain of anthrax, it isn't contagious, so the bacteria aren't likely to spread.

Despite all the worries about drug resistance, medical authorities agree that people with anthrax or likely exposure to its spores should be treated with antibiotics on both humanitarian grounds and to help maintain public calm. However, doctors and researchers do recommend several measures to limit antibiotic use:

• People should stop stockpiling Cipro and take it only on medical advice. Doctors, pharmacists and insurers should balk at unnecessary prescriptions.

• Farms should limit the use of antibiotics to protect healthy animals or boost their growth. The U.S. Food and Drug Administration has proposed banning enrofloxacin, a close cousin of Cipro given to chickens and turkeys.

• Foreign governments, including Mexico, should be pressured to stop over-the-counter sale of antibiotics.