Plague
Earlier today Xinhuanet.com reported that a fourth pneumonic plague patient is near death and one more is in serious condition in the town of Ziketan, a remote northwestern village in Qinghai Province in the Hainan Tibetan Autonomous Prefecture. 12 people have been hospitalized and three or four have died. Chinese officials have quarantined the town of about 10,000 and are killing rats and fleas to prevent further spread of the disease. Later today Xinhaunet.com reported that officials have now effectively controlled the plague.
Pneumonic plague infects the lungs and is caused by the bacteria Yersinia pestis. This bacteria also causes septicemic plague and bubonic plague -- the form of plague depends on the the route of transmission. Pneumonic plague is transmitted by aerosolized bacteria, which cause pneumonia, progressive organ failure, and often swift death if left untreated.
Because these bacteria are carried through the air in droplets, the disease can spread from humans to humans or animals to humans, and is considered highly contagious. If the infection is diagnosed quickly and antibiotics given promptly, patients will make a full recovery. The World Health Organization is working with Chinese officials and monitoring the plague outbreak.
The Center for Disease Control (CDC), has an interesting page on the history of the plague. Until Alexandre Yersin and Shibasaburo Kitasato determined the cause of the disease in 1894, many people died and many more attributed the massive deaths to the wrath of gods.
After the scientists identified the cause bacteria Yersinia pestis, people adapted to the fact that the disease spread between animals, often rats, via fleas. The mere sight of a dead rat sometimes causes people to flee their homes and towns. Plague can cycle for years between rats and fleas without infecting human populations, but inevitably, every few years an outbreak occurs. The CDC article notes that the catastrophic loss of life associated with historic plagues -- even today -- gives people a heightened fear of "the plague".
Zoonotic Disease Update
Plague is in the large group of zoonotic diseases that pass from animals to humans, or from humans to animals -- also called reverse zoonosis. In other zoonotic disease news, French scientists isolated a new group of HIV-1 from a Cameroon woman, which they're calling group P. The scientists found that this strain originated in gorillas rather than chimpanzees. The woman had recently moved to Paris from Cameroon and had tested seropositive for HIV-1 but didn't have signs of acquired autoimmune deficiency (AIDS). The researchers are tracking different strains of HIV virus, and they generally identify an unusual strain when AIDS symptoms are present in someone who tests negative for the virus. In this case the opposite situation occurred.
Although various viral load tests were positive, the researchers tested the woman's viral DNA against the known groups of HIV-1, referred to as M, N, and O, and found that whatever virus she was testing positive for didn't match these groups. The researchers then sequenced the viral genome and performed evolutionary analysis, which showed that the virus sequence was closer to a known simian immunodeficiency virus (SIV) found in gorillas, called SIVgor, than to the chimpanzee SIV from which HIV-1 groups M, N, and O derived.
Scientists who had analyzed the SIVgor virus recently found that it had the capacity to infect humans, however this is the first identified case. Scientists here knew the results of both viral testing and acquired immunodeficiency status which gave them the opportunity to identify the new strain, however; there may be other people infected with the same or similar gorilla derived viruses. Nature published the report.
Also this week, the scientists proposed in Proceedings for the National Association of Sciences (PNAS) that malaria may have originated in chimpanzees.
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Acronym Required writes frequently on infectious diseases such as malaria, H5N1, H1N1 and AIDS, and once on bats and Hanta virus.
