Human monkeypox

Daniel Di Giulio and Paul Eckburg's review¹ of human monkeypox in Africa is informative. Monkeypox is an important, emerging zoonosis and we applaud the authors' support for a vigorous research agenda. However, we wish to clarify some of Di Giulio and Eckburg's statements about the outbreak that occured in the USA in 2003.

Rabbits were not found to be enzootic hosts of the monkeypox virus during the 2003 outbreak. DiGuilio and Eckburg cite the first in a series of five reports on the monkeypox outbreak published in the Morbidity and Mortality Weekly Report (MMWR) as evidence that a rabbit became infected with the monkeypox virus after having been exposed to an infected prairie dog at a veterinary clinic.² They place emphasis on the virus being transmitted from one New World species to another and the increasing potential for establishment of an enzootic reservoir. These authors further assert that the infected rabbit transmitted the virus to a human being. This MMWR article described the association of an ill rabbit and a possible human monkeypox case; however, laboratory testing of rabbit necropsy specimens did not find monkeypox virus infection (Centers for Disease Control and Prevention, unpublished data). 1 month later the update published in the MMWR ³ correctly reported that the cases of monkeypox in human beings were associated with exposure to prairie dogs.

The case counts presented in Di Giulio and Eckburg's review was also derived from case totals released in an interim report.⁴ These numbers were compiled before completion of laboratory testing, follow-up interviews, and in some cases, clinical evaluations of people suspected of having had monkeypox. Updated case counts were published 1 week after those cited by Di Giulio and Eckburg.³

These authors' account of the introduction of monkeypox virus into the USA via a shipment of exotic rodents from Africa is not complete. The six species of African rodent referred to in the review were part of the suspect importation from Africa, but several other African non-rodent species, including palm civets, genets, and cusimanses, were present as well. The permissiveness and reservoir potential of these species for monkeypox virus is not known, but their presence in the shipment may prove noteworthy. Additional epidemiological and laboratory studies will address this matter.

Since the latest public-health update on the US outbreak of monkeypox,³ new laboratory test results have been developed and data collection and analysis continue. A comprehensive publication describing the epidemiology of this outbreak is forthcoming.