Pneumonic plague, a severe type of lung infection, is one of three main forms of plague, all of which are caused by the bacterium Yersinia pestis. It is more virulent and rare than bubonic plague. The difference between the versions of plague is simply the location of the infection in the body; the bubonic plague is an infection of the lymphatic system, the pneumonic plague is an infection of the respiratory system, and the septicemic plague is an infection in the blood stream.
Typically, the pneumonic form is due to a spread from infection of an initial bubonic form. Primary pneumonic plague results from inhalation of fine infective droplets and can be transmitted from human to human without involvement of fleas or animals. Untreated pneumonic plague has a very high fatality rate.
Since 2002, the World Health Organization (WHO) has reported seven plague outbreaks, though some may go unreported because they often happen in remote areas. Between 1998 and 2009, nearly 24,000 cases have been reported, including about 2,000 deaths, in Africa, Asia, the Americas, and Eastern Europe. Ninety-eight percent of the world's cases occur in Africa.
Pathology and transmission
Pneumonic plague can be caused in two ways: primary, which results from the inhalation of aerosolised plague bacteria, or secondary, when septicaemic plague spreads into lung tissue from the bloodstream. Pneumonic plague is not exclusively vector-borne like bubonic plague; instead it can be spread from person to person. There have been cases of pneumonic plague resulting from the dissection or handling of contaminated animal tissue. This is one type of the plague formerly known as the Black Death.
The most apparent symptom of pneumonic plague is coughing, often with hemoptysis (coughing up blood). With pneumonic plague, the first signs of illness are fever, headache, weakness and rapidly developing pneumonia with shortness of breath, chest pain, cough and sometimes bloody or watery sputum.
The pneumonia progresses for two to four days and may cause respiratory failure and shock. Patients will die without early treatment, some within 36 hours.
Initial pneumonic plague symptoms can often include the following:
Rapidly developing pneumonia with:
- Shortness of breath
- Chest pain
- Bloody or watery sputum (saliva and discharge from respiratory passages).
Prognosis and treatment
Pneumonic plague is a very aggressive infection requiring early treatment. Antibiotics must be given within 24 hours of first symptoms to reduce the risk of death. Streptomycin, gentamicin, tetracyclines and chloramphenicol are all effective against pneumonic plague.
Antibiotic treatment for seven days will protect people who have had direct, close contact with infected patients. Wearing a close-fitting surgical mask also protects against infection.
The mortality rate from untreated pneumonic plague approaches 100%.
In September of 1994, India experienced an outbreak of plague that killed 50 and caused travel to New Delhi by air to be suspended until the outbreak was brought under control. The outbreak was feared to be much worse because the plague superficially resembles other common diseases such as influenza and bronchitis; over 200 people that had been quarantined were released when they did not test positive for the plague.  All but two of the deaths occurred around the city of Surat.
The People's Republic of China has eradicated the pneumonic plague from most parts of the country, but still reports occasional cases in remote Western areas where the disease is carried by rats and the marmots that live across the Himalayan plateau. Outbreaks can be caused when a person eats an infected marmot or comes into contact with fleas carried by rats. A 2006 WHO report from an international meeting on plague cited a Chinese government disease expert as saying that most cases of the plague in China's northwest occur when hunters are contaminated while skinning infected animals.
The expert said at the time that due to the region's remoteness, the disease killed more than half the infected people. The report also said that since the 1990s, there was a rise in plague cases in humans—from fewer than 10 in the 1980s to nearly 100 cases in 1996 and 254 in 2000. Official statistics posted on the Chinese Health Ministry's Web site showed no cases of plague in 2007 and 2008. In September 2008, two people in east Tibet died of pneumonic plague.
A recent outbreak of the disease in China began in August 2009 in Ziketan Town located in Qinghai Province. The town was sealed off and several people died as a result of the disease. According to spokesperson Vivian Tan of the WHO office in Beijing, "In cases like this [in August 2009], we encourage the authorities to identify cases, to investigate any suspicious symptoms among close contacts, and to treat confirmed cases as soon as possible. So far, they have done exactly that. There have been sporadic cases reported around the country in the last few years so the authorities do have the experience to deal with this."
In September 2010, there were five reported cases of pneumonic plague in Tibet.[where?]
In July 17, 2014, Chinese media reported one case found in Gansu.
In August 2010, Peru's health minister Oscar Ugarte announced that an outbreak of plague had killed a 14-year-old boy and had infected at least 31 people in a northern coastal province. The boy died of bubonic plague on 26 July 2010. Ugarte stated that authorities were screening sugar and fish meal exports from Ascope Province, located about 325 miles (520 km) northwest of Lima, not far from popular Chicama beach. Most of the infections in Peru were bubonic plague, with four cases of pneumonic plague.
The first recorded plague outbreak in Peru was in 1903. The last, in 1994, killed 35 people.
An outbreak of plague in November 2013, occurred in the African island nation of Madagascar. As of 16 December, at least 89 people were infected, with 39 deaths with at least two cases involving pneumonic plague—however, it was reported later that as many as 90% of cases involved pneumonic plague. The World Health Organization and Institut Pasteur were both involved in administering antibiotic compounds and attempting to stop the spread of the disease, through closing all sea and airports at first instance of infection.
Recent notable cases
On July 10, 2014, in an online news story article, by Keith Coffman of Reuters, featured on the MSN U.S. News website, it was stated that a Colorado man, whose condition the report said was not known, had been diagnosed with the pneumonic plague. The man was found to have the disease after the family dog died unexpectedly and a necropsy conducted on it revealed it had died from the disease, which is spread when fleas which have been hosted by rodents (mostly prairie dogs) spread to another nearby host once the original one dies. The plague is found in the western U.S., according to the CDC.
As of July 18, 2014, three more cases were reported in Colorado. However, the outbreak appears to be over, according to state officials.
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