Until now, health officials investigating the weeklong outbreak in the United States have said that the virus was being spread by pet prairie dogs. But the disease can also be transmitted from one person to another, something that has happened in Africa.
Patrice M. Skonieczny, infection control coordinator at St. Francis Hospital in Milwaukee, said a nurse developed monkeypox symptoms after caring for a patient with a possible case of the disease.
In another case, Dr. John Melski, a dermatologist at Marshfield Clinic in Marshfield, said a medical assistant is suspected of getting the disease after helping treat a 3-year-old girl May 22. The girl was later diagnosed with monkeypox.
"She held the child when the child was brought in and may have had contact with the infected lesion," Melski said. He said the medical assistant's boyfriend has some similar symptoms, but it's unknown how he may have gotten sick.
"If I were a family member of somebody who had monkeypox, I would want to know you really need to practice precautions within the home," Melski said.
State epidemiologist Jeff Davis said Thursday that confirmation of those cases would mark the first known human-to-human transmission of the virus in the nation.
Skonieczny said the nurse at St. Francis was wearing protective clothing, including a mask, gloves and a gown, when she cared for the south Milwaukee pet distributor being treated for possible monkeypox.
The nurse developed flu-like symptoms, including a transient rash, several days later, Skonieczny said. The nurse, who health officials declined to identify, has been isolated at home at the request of health officials.
Davis said health officials and scientists haven't confirmed the presence of the monkeypox virus in the worker, but they suspect it and are testing tissue specimens.
The medical assistant developed chills and sweats Tuesday, and swabs from her throat were obtained for testing by federal officials, the doctor said. The woman has not been hospitalized and her condition is being monitored, he said.
As of Thursday, U.S. health officials had confirmed a total of 12 human cases of the disease: four each in Wisconsin, Indiana and Illinois. Also, 54 possible cases had been reported - 25 in Indiana, 17 in Wisconsin, 11 in Illinois and one in New Jersey.
No one has died from the disease in the United States, but at least 14 patients with symptoms have been hospitalized, including a child with encephalitis, or brain inflammation, the Centers for Disease Control and Prevention reported. No details about the child's condition were released.
Davis said the animals appear to be infecting people through bites or when people touch discharges from the prairie dogs and then rub their eyes or noses. The Wisconsin health worker may have contracted the illness before word of the monkeypox outbreak became public last week, Davis said.
Monkeypox, a disease never before seen in the Western Hemisphere, is related to smallpox but is not as lethal. It causes pus-filled blisters, rashes, chills and fever.
Federal health officials have traced the outbreak to prairie dogs distributed by Phil's Pocket Pets of Villa Park, Ill. The prairie dogs were apparently infected at the business by a Gambian giant rat, officials said.
Prairie dogs from Phil's Pocket Pets may have been sold to numerous buyers in 15 states, according to investigators.
On Wednesday, the government recommended smallpox shots for people exposed to monkeypox. The vaccine can prevent the disease up to two weeks after exposure to the virus and is most effective in the first four days.
But some health officials are wary. In rare cases the vaccine can cause serious and even have deadly side effects.