Health scares have a way of galvanizing public attention on a single threat, and at least six contagions have generated waves of public unease over the past 13 years, experts say.

Ebola is the latest.

Public alarm about a virus that has affected fewer than 20 people outside of West Africa is leading to new rules and fears of a deadly disease.

The Ebola scare triggered tough quarantine rules in New York, New Jersey and Illinois, and monitoring requirements in Florida. Health care workers returning from West Africa must be confined for 21 days, a demand agencies like Doctors Without Borders believe may adversely affect their ability to attract new volunteers. Civil liberties groups say quarantines may impinge on citizen's rights.

"Fear is contagious," said Dr. Victor Fornari, director of child and adolescent psychiatry at Zucker Hillside Hospital in Glen Oaks, Queens. His cure: Limit exposure to the sources of the scares, such as cable news, the Internet and social media.

"We are really a global community now," said Dr. Alan Manevitz, a psychiatrist at Lenox Hill Hospital in Manhattan. "Any kind of emerging medical issue, political concern or environmental problem anywhere in the world can impose complex demands on the collective psyche.

"These things challenge our sense of well-being," Manevitz said, adding, the overall sense of fear triggers a primordial fight-or-flight response. "People want to take action, do something," he said.

Dr. Aaron Glatt, chief executive of Mercy Hospital in Rockville Centre and a specialist in infectious diseases, said some people see dramatic news footage of mass graves of Ebola victims in three West African countries and imagine a rapid global spread of the virus.

"You have movies about viruses and end-of-the-world doom," said Glatt, a spokesman for the Infectious Diseases Society of America. Instead, it's better to stay riveted on sound public health advice from credible sources, he said.

"People are refusing to go to the Dallas hospital where the patient was treated for Ebola because they think they're going to catch it," Glatt said. A Liberian national died earlier this month and two nurses who treated him contracted the infection. But the Dallas hospital is not an Ebola source, he said. Viruses, scientists say, are fragile entities and cannot exist outside living cells.

"The average American probably hadn't heard of Ebola until two months ago. But people are concerned because they think it can affect them," Glatt said.

Ebola isn't the only health scare that has caused a nationwide outbreak of fear.

2009: Fear of pandemic flu led to an upsurge in Internet sales of antiviral medications, inspiring black-market profiteers to bootleg knockoffs to capitalize on mass fear of the influenza strain.

2005: Bird flu caused worldwide panic even though scientists had found the virus wasn't easily transmitted person to person. Bird flu, experts said, was a deadly pandemic among wild birds -- not the 21st century's version of the Black Death, a flea-transmitted plague that devastated Europe in the 1300s.

2003: SARS emerged in China and spread via airline passengers to Canada, touching off global panic. The fear grew out of the numbers: 7,000 people affected in China, where more than 750 died. The virus was transported to Canada by infected airline passengers, then infected about 250 Canadians and killed 44. But SARS vanished almost as quickly as it had appeared. The fear nevertheless lingered.

2002: The Bush administration warned of a potential comeback of smallpox, the only disease to be completely wiped off the planet. The claim was based on faulty intelligence that Saddam Hussein's Iraq regime harbored lab vials of the virus as part of a cache of bioterror weapons. That turned out not to be true.

2001: Anthrax-by-mail, a scare that began one week after the 9/11 terror attack on the Twin Towers. Letters filled with anthrax spores were mailed to several media outlets and two federal lawmakers. Five people died and 17 were sickened, but the national panic caused such a run on the antibiotic Ciprofloxacin -- Cipro -- that supplies ran low for legitimate medical care.

Experts say health scares are fueled not only by fear but also by junk science -- such as the current claim from some nonmedical pundits that Ebola has already evolved into an airborne form.

"I don't know why the pundits think they know more than we do," said Dr. Vincent Racaniello, a professor of microbiology and immunology at Columbia University.

Racaniello, a virologist, said viral evolution doesn't occur overnight and that the key strain, Ebola Zaire, hasn't changed since its discovery in 1976.

Glatt said scares have an element of excitement, which draws people to news about them, while more widespread but commonplace health conditions don't get enough attention.

"You talk about an illness like hypertension, but nobody's listening. There's an epidemic of hypertension right now. But they can't hear you."