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Last Updated

01 Jul 2003

Source: Newsday, July 1, 2003

Highly Infectious, Hardly Understood

Data lacking on monkeypox virus

By Delthia Ricks, STAFF WRITER

Even though the current monkeypox outbreak marks the first time the virus has caused infections in the West, the virus itself has been in the United States for years, under study in classified federal and military laboratories, scientists have acknowledged.

Stocks of the highly infectious virus have been maintained for at least a decade, used mostly as a stand-in for the more virulent smallpox pathogen in what is described as highly contained laboratory research. Working with the monkeypox microbe poses fewer risks to scientists than the smallpox virus, experts say.

Despite years of research, scientists admit that the monkeypox virus and the infection it causes largely remain a mystery because so little data have been collected. The current outbreak will add to the overall understanding, scientists say, but questions will persist regarding how many species carry it, how people catch it and whether it's undergoing mutations in the wild.

"We really don't know very much about this virus," said Dr. Joel Breman, a senior scientist at the National Institutes of Health, and a former chairman of the World Health Organization's monkeypox study committee.

"We don't know all of the ways in which humans acquire it and we don't know the host reservoir of the virus," added Breman, a senior scientist in the NIH's Fogarty International Center.

Even though the virus is called monkeypox, Breman said, "people have built a story" around the virus originating in monkeys. It's not known if the virus first arose in monkeys, he said, though it is likely that it may have originated in rodents in Africa and then was transmitted to monkeys.

Most of the work involving the microbe is under way at the U.S. Army Research Institute for Infectious Diseases in Fort Detrick, Md. Smaller studies are being conducted at the Centers for Disease Control and Prevention. Both have high-containment labs built to handle extremely dangerous agents. Laboratories nationwide are ranked on a scale of one to four, four being the highest level for the most dangerous pathogens, such as smallpox, Ebola and Lassa fever viruses.

Because monkeypox is not as virulent, scientists are studying it in a biosafety level-3 laboratory, CDC experts say.

Breman, who distinguished himself more than two decades ago by diagnosing simultaneous cases of smallpox and monkeypox in Central Africa, said much of the military and government work is focused on antivirals and developing an animal model for monkeypox. Another critical area of research, he underscored, focuses on developing a safer smallpox vaccine.

Scientists deem work on the monkeypox virus crucial, Breman added, because it can lead to a better understanding of the smallpox pathogen, which can be used as an agent of bio-terror.

Federal health officials have been investigating 79 possible monkeypox cases in eight states, an outbreak first reported June 9. Twenty-nine cases of the infection have been confirmed, the Centers for Disease Control and Prevention reported last week.

Two cases have been serious, the CDC reported, both involving children. One, a young girl whose infection progressed into an inflammatory brain condition, improved and was discharged after 14 days in a hospital.

CDC director Dr. Julie Gerberding said that state and local health agencies did not suspect bioterrorism when they noticed the infections because all were associated with prairie dog bites. Monkeypox, like smallpox, is typified by flu-like symptoms and crusting, pus-filled sores. The animals were believed to have been penned near monkeypox-infected African rodents, the likely source of the virus.

Though researchers first identified the monkeypox pathogen in 1958, science never developed volumes of data on the virus comparable to that of other killer pathogens, said former military virologist Donald Smee, now at Utah State University in Logan.

The virus doesn't aerosolize like smallpox, Smee said, which means it can't be spread through sneezing and coughing. And contrary to earlier reports, Gerberding added, none of the prairie-dog triggered monkeypox infections have been secondarily transmitted person to person.

"It doesn't seem to transmit as readily as smallpox, added Smee, who no longer works directly with the virus but is aiding military scientists in developing a medication to treat monkeypox or smallpox infections.

"An outbreak with monkeypox isn't as catastrophic an event as with smallpox. It dies out after infecting a few people," Smee said. Smallpox infections by comparison can spread like viral wild fire because of their potential for aerosol transmission.

"But that doesn't mean monkeypox is a simple infection. The infection is caused by a very lethal virus," Smee said.

Smee's studies are focused on the powerful antiviral drug called cidofovir. Though the drug is currently approved, it is administered only intravenously. Smee is working on an experimental oral form, which would be useful in the event of bioterror involving the smallpox virus.

Scientists who have been working on developing an animal model for monkeypox, a species that could be infected but not killed by the pathogen, were surprised about the prairie dog infections. Prairie dogs are carriers but remain unharmed by the virus.

"It is exceedingly important to study the infected prairie dogs," Breman said, because the chubby- cheeked rodents may open windows into a better understanding of the monkeypox virus.