Monkeypox Often Affects Lymph Nodes

NEW YORK (Reuters Health) - About three quarters of patients with monkeypox have affected lymph nodes, a condition that is rare in cases of smallpox or chicken pox, investigators report in two articles in the journal Clinical Infectious Diseases. Other common features of monkeypox, in addition to rash and fever, include chills, sore throat, headache and muscle pain.

Considered a possible agent of bioterrorism, it is important to recognize signs and symptoms of monkeypox and to differentiate it from other pox virus infections, research teams led by Dr. Matthew J. Kuehnert and Dr. Aysegul Nalca point out.

Kuehnert, from the Centers for Disease Control and Prevention in Atlanta, and his colleagues analyzed records of 34 patients who were treated for monkeypox during an outbreak in the US in 2003. The primary source of the infection was traced to pet prairie dogs that had been housed with imported rodents from Ghana.

Most patients reported that rash, fever, chills, and lymph node swelling were the first symptoms to appear. Abnormal laboratory findings included disturbances in liver tests, high white blood cell counts, and low platelet levels.

In contrast to what is seen in cases of chickenpox, none of those with monkeypox experienced excessive clotting throughout the body and there were no deaths. However, nine patients were hospitalized. In addition to the common symptoms, those hospitalized were also likely to experience mouth sores, difficulty swallowing, nausea and vomiting.

In the second report, Nalca, from the United States Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland, and colleagues point out that laboratory confirmation of monkeypox is required for a definitive diagnosis.

Smallpox vaccination is believed to be protective against monkeypox virus. The CDC recommends vaccination for those who may be exposed to monkeypox virus, up to 14 days after exposure. Patients should be isolated until scabs fall off and throat swab results are negative.

Nalca's team notes that the antiviral drug cidofovir is effective in treating the infection in laboratory animals. However, they add, "the risk of drug therapy must be examined and weighed against the severity of poxvirus disease."

SOURCE: Clinical Infectious Diseases, December 15, 2005.