Rare diseases that have long been off the American radar screen still pose a considerable threat, experts said, in large part because the nation's medical community is ill-prepared to diagnose, treat and contain sudden outbreaks.
"One of our biggest fears is that many of the diseases which have fortunately been wiped out by immunization would be very difficult to diagnose," said Dr. Bradley Connor of the New York Center for Travel and Tropical Medicine.
"The world is becoming a smaller place. You don't have to leave the United States to get traveler's diarrhea. It comes to you," Connor said.
While the global economy increases the risk of diseases traveling via international tourists or imported foods, doctors also fear bioterrorism could threaten Americans' health.
Smallpox, the plague and anthrax are now foreign to the United States because of medical advances, but they could come back through an act of terrorism.
Dr. Sam Katz of Duke University said the threat of a smallpox outbreak from bioterrorism is "very real."
Katz said Iraq and Russia are widely thought to have reservoirs of smallpox, which could be disseminated through aerosol spray. Where exactly the supply is and who possesses it is uncertain, he said.
"We live, unfortunately, in a world where bioterrorism is increasingly a concern," Katz said.
The last known case of smallpox was in Somalia in October 1971. Therefore, few doctors practicing today would be able to recognize the disease's symptoms, Katz said.
"Most of us who may have seen a case of smallpox are in our 70s. The people who are in emergency rooms and elsewhere may have some difficulty; they might mistake it as chicken pox or something," he said.
Katz said the government should contract with a pharmaceutical firm to manufacture a smallpox vaccine for public use. For the last 15 to 20 years, only laboratory workers who could come into contact with the virus have received the vaccine, he said.
Specialists are keeping an eye on several diseases that could potentially arrive on U.S. shores through bioterrorism or travel.
One example is Dengue Fever, a viral illness transmitted by mosquitoes that causes so-called "breakbone fever." Connor said it "literally feels like your bones are breaking."
The disease is currently found in the Caribbean and across Asia, but doctors worry that increased development will lead to infected mosquitoes showing up in semi-urban areas. Consequently, Americans who travel to these areas could bring the disease home.
GeoSentinel, an information network operated by the International Society of Travel Medicine, attempts to prevent isolated outbreaks of rare diseases in distant lands from turning into epidemics by disseminating disease reports from the federal Centers for Disease Control and Prevention in Atlanta worldwide.
For example, a few months ago Connor saw a patient with leptospirosis, a disease not common in the United States. The patient had recently been at the Eco-challenge sports competition in Borneo.
Connor contacted GeoSentinel and found there were patients in England and Canada who had returned from the Eco-challenge with similar symptoms. GeoSentinel then put out an alert to all attendees of the event so they could seek treatment.
"If we didn't have this network, isolated doctors in isolated countries would be seeing isolated cases," Connor said.
Doctors suggest that travelers seek medical advice before traveling abroad, and be sure to tell their health-care provider where they've been the past few months if they get ill, since diseases such as malaria can have an incubation period of up to several months.
"People die of malaria because physicians don't think to make the diagnosis," Connor said. "Travel history is a very important part of medical history."
Doctors also are pressing the government to maintain funding and public education for diseases that were once threatening and have now declined.
Dr. Henry Blumberg of the Emory University School of Medicine said the sudden boom of tuberculosis in the mid-1980s to early 1990s should serve as a lesson to the medical community not to let its guard down.
Just when doctors assumed tuberculosis was completely wiped out, it reappeared in a multidrug-resistant form in many HIV-positive patients.
"The rates were going down, so people didn't think (tuberculosis) would be a problem. The federal funding for (it) was cut and essentially wiped out," Blumberg said.
But outbreaks began when doctors misdiagnosed symptoms in HIV patients, and reversing the damage was ultimately a costly public health problem.
"It took $1 billion in New York City alone over a number of years to rebuild the public health infrastructure," Blumberg said.