Pneumonic plague

A scanning electron micrograph depicting a mass of Yersinia pestis bacteria.

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 septicaemic plague is an infection in the blood stream.

Typically, 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.

Epidemiology

Since 2002, the World Health Organisation (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. 98 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 formerly known Black Death.^[1] It could kill 90%–95% of a population if the victims cough and pass on the bacteria.

Symptoms

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.^[2]

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:

• Fever
• Weakness
• Headache
• Nausea

Rapidly developing pneumonia with:

• Shortness of breath
• Chest pain
• Cough
• 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.^[2] Streptomycin, gentamicin, tetracyclines and chloramphenicol are all effective against pneumonic plague.

Antibiotic treatment for 7 days will protect people who have had direct, close contact with infected patients. Wearing a close-fitting surgical mask also protects against infection.^[2]

The mortality rate from untreated pneumonic plague approaches 100%.^[3]

China

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.^[4]

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.^[5] Official statistics posted on the Chinese Health Ministry's Web site showed no cases of plague in 2007 and 2008.^{[citation needed]} In September 2008, two people in east Tibet died of pneumonic plague.^[6]

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.^[4][7] 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."^[8]

In September 2010, there were 5 reported cases of pneumonic plague in Tibet.

Peru

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.^[9]

The first recorded plague outbreak in Peru was in 1903. The last, in 1994, killed 35 people.^[10]

Madagascar

An outbreak of plague in November, 2013, occurred in the African island nation of Madagascar.^[11] As of 16 December, at least 89 people were infected, with 39 deaths^[12] with at least two cases involving pneumonic plague- however, it was reported later that as many as 90% of cases involved pneumonic plague.^[13] The World Health Organisation 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 November 2, 2007, wildlife biologist Eric York died of pneumonic plague in Grand Canyon National Park. York was exposed to the bacteria while conducting a necropsy on a mountain lion carcass.^[14]

See also

• Bubonic plague
• Septicemic plague

References

External links

• Facts about Pneumonic Plague. Centers for Disease Control and Prevention.