The germ caused two cattle herders to suffer fever, swollen lymph nodes, and painful boils on their hands and arms in 2013. It happened in a rural area in the country of Georgia. They recovered in a matter of weeks. A third case in a cattle owner in 2010 was later discovered.
The new virus has been named Akhmeta after the area where it was first detected. A report on the virus by health officials in Georgia and the United States was published online Wednesday in the New England Journal of Medicine.
It doesn't seem to be a public health threat, and likely was around for many years before it was identified, said Dr. Donald "D.A." Henderson. He is a renowned smallpox expert at the University of Pittsburgh who was not involved in the Akhmeta virus research.
The new germ is from a group of viruses that cause cowpox, monkeypox and smallpox, which have similar symptoms including boils.
"The good news is that it seems less severe" than monkeypox and smallpox, said Dr. Neil Vora of the U.S. Centers for Disease Control and Prevention, the lead author of the new report.
It is most similar to cowpox, a rarely-seen disease. Cowpox has been in Europe for centuries, and health officials have been on the lookout for cowpox-like diseases in Georgia and nearby countries, Vora said.
Monkeypox, also rare but sometimes fatal, has been seen mainly in Africa. Smallpox was one of the deadliest diseases in history before a global vaccination campaign led to its eradication 35 years ago.
Scientists think the new virus spreads through contact with infected animals, not person-to-person. The three Georgia infections are believed to be from cows, but the cows probably got it from smaller animals, Vora said.
The researchers trapped small animals in the area and found signs of possible past infection in the blood of three shrews and nine rodents.