An outbreak of an unusual virus shows up in the U.S.
Monkeypox is usually found in west Africa. This is the first time the disease has been seen in the western hemisphere.
So far the disease, which is similar to smallpox has been confirmed in four patients in Wisconsin. Health officials are watching for it in more than 20 other people in Wisconsin, Indiana and Illinois. They believe humans got it from pet prairie dogs.
It's called Monkeypox because it originated in primates, but rabbits and rodents like prairie dogs can also carry the virus. And for the first time, it's popping up in the western hemisphere.
Monkeypox is related to the smallpox virus. It's usually confined to the rain forests of central and western Africa. The cases in the midwest apparently jumped to humans from pet prairie dogs who got it from a diseased Gambian rat at a pet distributor in Chicago.
At the Sedgwick County Zoo, Monkeypox is not a concern. Zoo officials say they have a very healthy population of prairie dogs.
Dr. Sandy Wilson at the Sedgwick County Zoo says, "Hopefully it's going to be very short-lived and not spread beyond the original animals."
Veterinarians say they occasionally see new viruses in the U.S., and they can end up in humans. A recent example is West Nile Virus.
Dr. Wilson says, "Much like West Nile Virus was something new to us a couple of years ago that on the other hand is probably here to stay.
But monkey pox is probably not going to be a big problem."
The Monkeypox virus causes a rash illness similar to smallpox, but less infectious. Along with a rash, symptoms include fever, headaches and chills. Monkeypox is not usually deadly in humans.
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Symptoms can be accompanied by diarrhea, swollen lymph nodes, a sore throat and mouth sores. In some cases, a victim may experience trouble breathing. Symptoms are at their worst for 3 to 7 days, after which the fever lessens and blisters begin to form crusts.
Monkeypox is a viral disease with a clinical presentation in humans similar to that seen in the past in smallpox patients. Smallpox no longer occurs, following its worldwide eradication in 1980, whereas monkeypox is still seen as a sporadic disease in parts of Africa.
The virus responsible for monkeypox is related to the virus that used to cause smallpox (both are orthopoxviruses). Vaccination against smallpox (no longer necessary) also gave protection against monkeypox. Before the eradication of smallpox, vaccination was widely practiced and protected against both diseases. However, children born after 1980 have not been vaccinated against smallpox and are likely to be more susceptible to monkeypox than older members of the population. The death rate from monkeypox is highest in young children, reaching about 10%.
Most cases occur in remote villages of Central and West Africa close to tropical rainforests where there is frequent contact with infected animals. Monkeypox is usually transmitted to humans from squirrels and primates through contact with the animal's blood or through a bite.
Following reports of ongoing cases of human monkeypox in the Democratic Republic of the Congo ("DRC", formerly Zaire) representing a new pattern of the disease, the Ministry of Health in DRC and the World Health Organization (WHO) organized two investigations in February and October 1997.
In the past, an outbreak of monkeypox in DRC would have been limited to the village and would not last long because it did not spread extensively after the first patients recovered. However, the present study indicates that monkeypox disease is changing its pattern of infection in humans. The outbreak had a much higher rate of person-to-person transmission than seen previously, and spread through many generations of transmission, thus maintaining the outbreak for more than a year.
Previous studies over a twenty-year period had shown that the rate of transmission of monkeypox within households was low, suggesting that the disease had a low potential for transmission from person to person. Outbreaks were generally self-limiting after one or two sequential transmissions. However, the two recent WHO studies have to-date shown that:
The ending of vaccination programs against smallpox in the late 1970's has probably led to an increase in susceptibility to monkeypox and could explain the larger size of the most recent outbreak, the higher proportion of patients aged 15 and over, and the spread through many generations of transmission.
WHO is concerned that monkeypox could pose a public health problem in this region of DRC and therefore vigilance must be maintained by strengthening detection systems for monkeypox and completely investigating future outbreaks.
Further WHO studies are planned in the region to determine the need for additional risk-reduction measures.
In May 1996, the 49th World Health Assembly decided that the last remaining stock of smallpox virus held in two research centers in the Russian Federation and the United States of America should be destroyed as the last step in the complete and final global elimination of smallpox. It also decided that WHO would keep 500 000 doses of smallpox vaccine (which is also effective against monkeypox). The smallpox vaccine seed virus (vaccinia virus strain Lister Elstrea) will be maintained in the WHO Collaborating Centre on Smallpox Vaccine at the National Institute of Public Health and Environmental Protection in Bilthoven, Netherlands, so that new stocks of vaccine can be produced if needed.