WASHINGTON, April 26 (UPI) -- The anthrax letter attacks in 2001 are not the first time an infectious agent has been spread through the mail. A recent article in a scientific journal describes two outbreaks of smallpox in 1901 that were attributed to infected letters, and bioweapon experts said it is possible terrorists could spread the deadly disease in this manner today.
Charles Ambrose, the author's article and a microbiologist at the University of Kentucky School of Medicine in Lexington, noted that one of the outbreaks was attributed to infected letters sent from the United States to England -- a trans-Atlantic trip that at the time had to be made by boat. This suggests the virus may be able to survive extended periods in transit and raises the possibility of terrorists sending an infected letter into the United States from abroad.
Ambrose's article appears in the May issue of the journal Emerging Infectious Diseases.
Officials at the Centers for Disease Control and Prevention in Atlanta said it was unlikely smallpox could be transmitted through infected letters, but other bioweapon experts thought it could be done -- if samples of the deadly virus could be obtained in the first place.
"It would be really, really, really difficult" to infect people by sending the smallpox virus through the mail, CDC spokesman Von Roebuck told United Press International.
Bill Kournikakis, of Canada's Chemical Biological Defense Section in Medicine Hat, Alberta, disagreed with that assessment.
"If smallpox were available, then it would be possible to transmit it through the mail," he told UPI.
Kournikakis headed a study that showed anthrax could be transmitted through the mail several months prior to the 2001 attacks.
"Smallpox was well known for its virulence, contagiousness and stability (and) was able to survive for almost a year at room temperature in exudates or crusts from smallpox patients," he said. "It would most likely survive the postal system as well."
Smallpox kills about a third of those infected by the virus. Symptoms include fever, aches and the characteristic pox or raised bumps all over the body that form scabs and can leave disfiguring scars.
William C. Patrick, former chief of the product development for the U.S. Army's biological warfare laboratories at Fort Detrick, Md., told UPI he thought it was possible smallpox could be distributed via mailed items.
"Smallpox could be sent through the mail and cause problems," said Patrick, who has served as a consultant to the FBI and the CIA.
Patrick noted although smallpox is not as stable as anthrax, "it's more infectious." Only about three to five individual virus particles are needed to cause a smallpox infection, compared to 8,000-10,000 spores of anthrax.
The bioterror experts consulted for this article said they consider the real barrier to an attack is obtaining the virus, not the mail system. The only known stocks of smallpox in the world reside at CDC headquarters in Atlanta and a lab in Russia. However, some bioweapons experts think North Korea and Iran also possess smallpox and there are concerns Russia may have leaked samples of the deadly pathogen to various countries.
Ambrose noted in his article there may be a second, unconventional source of smallpox in Russia in the Sakha Republic region in northeast Siberia -- one of the coldest inhabited regions on Earth. In 1991, bioweapons experts went searching for smallpox victims who had become frozen and mummified under the ice in the 19th Century.
The concern was terrorists could recover corpses, thaw them and gain access to smallpox, but searchers found no trace of the virus.
The United States could be very susceptible to a smallpox attack. Much of the U.S. population has not been vaccinated against smallpox -- routine vaccinations stopped in 1972 -- and it is unclear if those vaccinated prior to that still retain immunity from the deadly disease. President George W. Bush's plan to vaccinate healthcare workers and first responders against smallpox appears to have all but halted. Only a fraction of the anticipated 500,000 people targeted to be vaccinated received the medication.
Ambrose's article also cited an outbreak in Saginaw, Mich., involving 34 people and detailed in a 1901 issue of the New York Medical Journal. That outbreak appears to have originated in a Saginaw woman who developed smallpox after receiving a letter from her boyfriend, a soldier in Alaska who had written the letter while infected with the disease himself.
The other smallpox outbreak occurred at the headquarters of the Mormon church in Nottingham, England, Ambrose wrote. A report in the April 1901 issue of the British Medical Journal attributes that incident to letters from Salt Lake City, where hundreds of smallpox cases had been reported in recent months.
Dr. D.A. Henderson, professor of medicine at the Center for Biosecurity at the University of Pittsburgh Medical Center, said under normal circumstances there probably was very little, if any, risk of an infected person transmitting smallpox through the mail.
He said it was highly possible the cases described in the medical journal articles had not been properly investigated and there could have been other ways people became infected that did not involve contaminated letters. When he was involved in efforts to eradicate smallpox globally, he said, no instances were ever reported of infections that could be traced back to infected mail items.
Henderson did say he thought it was possible terrorists could transmit smallpox through the mail by aerosolizing the virus, similar to what was done in the anthrax attacks, which infected 18 people and killed five.
"They could do that, oh yeah, no question," Henderson told UPI.
He said it was less likely to happen with smallpox than with anthrax, however, due to difficulties of obtaining the virus in the first place, the technical knowledge required to work with it, and the dangers of self-infection.
Henderson noted, however, officials involved in the Russian Bioweapons program have admitted in recent years they produced very fine, tiny-particle smallpox and conducted outdoors experiments with it in 1971. He said it is not known whether the efforts infected anyone, but it demonstrates the feasibility of aerosolizing the deadly virus.
Henderson said if smallpox was stabilized properly, it probably could survive a trip through the mail system, "but it wouldn't survive as well as anthrax."
Bob Anderson, a spokesman for the U.S. Postal Service, said in terms of precautionary measures to prevent biological weapons from being spread through the mail system, the only monitoring systems in place test for anthrax.
"The system is expandable -- meaning the equipment is capable of being configured to test for the presence of other biohazards in the mail -- but there are no plans to do so at this time," Anderson told UPI.
The Postal Service also irradiates some federal mail to kill potential bioweapons, but this process is used only on government mail headed for federal agencies in the Washington area, he said.
Henderson said he did not know if irradiation would kill the smallpox virus.
Steve Mitchell is UPI's Medical Correspondent. E-mail: email@example.com