American authorities are taking the prospect of bioterrorism more seriously these days — but even as they take care of one threat, plenty of others are lying in wait.
Last week, the Bush administration unveiled a plan to make the smallpox vaccine available to all 280 million Americans, in advance of any possible attack. Smallpox is probably the biological threat that causes the most concern among public health officials — because it is highly virulent, kills one-third of its victims, and can leave survivors scarred and seriously ill.
Smallpox may not be the biological threat that comes first to most Americans' minds. Anthrax remains a scare as authorities still do not know who sent anthrax through the mail last year, which killed five people.
And then there's West Nile, which was first discovered in the United States more than three years ago. Though spread primarily by mosquitos, at least one prominent lawmaker suggests the real cause of West Nile may be something more ominous — a planned bio-terror attack.
Plus, other potential biological threats exist that can be used to serve terror, scientists say.
"Theoretically, anything could be introduced," said Jacqueline Cattani, director of the Center for Biological Defense at the University of South Florida College of Public Health in Tampa.
Said Dr. John Clements, chair of microbiology and immunology at Tulane University in New Orleans: "We're going to see a lot of things we haven't seen before."
Ticking Time Bombs
Even before the clamor over smallpox's potential as a bio-terror weapon, scientists raised the alarm about the growing number of potent and easily transmittable diseases.
One of the most urgent growing threats is multi-drug resistant tuberculosis (MDR-TB), which is caused by an organism that is essentially the same as the one that causes regular TB — but has developed an immunity to the antibiotics usually used to treat it.
Scientists fear a sufferer of MDR-TB could be used as a sort of human germ bomb, a disease passed from one person to the next and the next. And it's not the only disease that could be used this way.
Victor Weedn, of the BioMedical Security Institute in Pittsburgh, cites the 1918 Spanish Flu pandemic — when a version of the virus unexpectedly emerged and killed 200,000 in the United States within a month.
"There are emerging diseases all the time," he said. And the modern world's ease of travel means that such diseases can have an even greater impact.
dMoreover, these highly virulent diseases don't necessarily need to use a human being as a host to have an impact, said Stephen Johnston of the University of Texas Southwestern Medical Center at Dallas. Examples include the foot-and-mouth disease that ravages livestock, or the crop disease known as rust.
Foot-and-mouth hasn't been seen in the United States since 1929, but when it struck Britain early last year, it shut down hundreds of that country's farms. According to official estimates, it cost the country's farming industry more than $12 million.
Fearing the Vector
Concern about West Nile grew significantly this year because of the big increase in fatalities. Last year, nine people died. This year, the death toll has reached at least 116.
And the disease has spread from the Northeast to most of the nation, prompting some to question just how West Nile came to be.
"I think we have to ask ourselves: Is it a coincidence that we are seeing such an increase in West Nile virus, or is that something that is being tested as a biological weapon against us?" Sen. Patrick Leahy, D-Vt., said in a radio interview earlier this month.
The public health community has generally dismissed the idea that West Nile virus could be used a bio-terror weapon. "There is no scientific evidence that West Nile virus is a result of bioterror," said Bernadette Burden, a spokesperson for the Centers for Disease Control and Prevention in Atlanta.
Scientists say Americans should get used to the disease — and certainly expect plenty more like it in the future. "We're going to live with West Nile for the rest of our lives," said Tulane University's Clements.
West Nile virus has been long known outside the United States, and probably appeared as a result of increased interconnectedness of the world, and fostered by the climate changes here, scientists say.
"It's a wonder it was never here before," said Michael Donnenberg, head of the Division of Infectious Diseases at the University of Maryland in Baltimore.
However, West Nile is not a very effective disease to use as a bioweapon, scientists say, because it is vector-borne — that is, it needs a host to move to another host, instead of simply being spread through the air.
With West Nile, mosquitoes become carriers when they feed on infected birds, and then transmit the infection to humans or other animals when they feed on them.
Like West Nile virus, dengue fever is a disease that was previously thought to be limited to the tropics, and whose symptoms include fevers, headaches, body aches and a rash. But dengue can be more devastating. One of its four distinct types is the severe and fatal hemorrhagic form, which causes breathing difficulties and bleeding from the nose, mouth, and gums.
Its route is much more direct, too. With dengue, the disease simply moves from human to mosquito to human.
"There's been a lot of debate on how dengue might be used as a bio-weapon," Cattani said. The CDC says between 100 and 200 suspected cases are introduced into the United States every year by way of travelers, and it was detected in South Texas as early as 1980.
Added Clements: "I think it's going to be more serious than West Nile."
Nature Still Trumps Man
Another disease that could be used as a bio-terror agent is hantavirus, also a vector-borne disease spread by the urine, droppings and saliva of rodents.
Early symptoms include fatigue, fever and muscle ache. Sufferers who go untreated experience coughing and shortness of breath, and eventually die of respiratory failure after their lungs fill with fluid.
And after hantavirus, scientists told ABCNEWS infectious diseases like plague, cholera and typhoid are potential threats.
These diseases are for the most part easily kept at bay by cleanliness, but they could also be genetically altered to make them more potent, in the way that multi-drug-resistant TB is, said Samuel Watson, a director at University of Pittsburgh's Graduate School of Public Health.
Hantavirus, in fact, is classified by the CDC as a Category C biological agent and threat because it could be "engineered for mass dissemination because of availability, ease of production, and potential for high morbidity."
Today's most common diseases of course were discovered independent of terrorists. "It's said scientists discover [at least] one new disease a year," said Weedn.
Increased contact with nature brought us Lyme disease in 1975. Indoor living and poor ventilation brought us Legionnaires' disease in 1976. Better testing methods found Campylobacter in 1977. And modern methods of meat processing have introduced new forms of E. coli over recent years.
"They say in Africa, there are viruses we don't even have tests for. It's inevitable that we'll find surprises in the future," Cattani said.