Plague (disease)

Plague is an infectious disease caused by the bacterium Yersinia pestis. Historically, it has been responsible for widespread pandemics with high mortality rates, the most famous being the Black Death in the 14th century, which resulted in the deaths of an estimated 75-200 million people across Europe, Asia, and Africa. Plague is primarily a disease of rodents, transmitted to humans through the bite of infected fleas, direct contact with infected tissues or fluids, or inhalation of infected respiratory droplets.

Types of Plague

There are three main forms of plague, each presenting with different symptoms:

1. Bubonic Plague: The most common form, characterized by the sudden onset of fever, headache, chills, and weakness, followed by the swelling of lymph nodes (buboes), which become painful and can turn into open sores.

2. Septicemic Plague: Occurs when the infection spreads to the bloodstream. Symptoms include fever, chills, extreme weakness, abdominal pain, shock, and potentially bleeding into the skin and other organs. This form can arise as a complication of bubonic plague or independently by direct infection through the bloodstream.

3. Pneumonic Plague: The most virulent and least common form. It affects the lungs and can be transmitted from person to person through airborne droplets. Symptoms include rapid onset of fever, headache, weakness, and rapidly developing pneumonia, with shortness of breath, chest pain, cough, and sometimes bloody or watery sputum.

Transmission

Plague is primarily a zoonotic disease, with rodents being the most common reservoir. The disease is transmitted to humans by the bite of an infected flea, direct contact with contaminated fluid or tissue, or inhalation of infected respiratory droplets. Human-to-human transmission is most common in the case of pneumonic plague.

Diagnosis

Diagnosis of plague is based on clinical symptoms and confirmed by laboratory tests. These tests can include examination of blood or lymph node samples for the presence of Yersinia pestis bacteria, serologic tests, and cultures of respiratory secretions in cases of suspected pneumonic plague.

Treatment

Early treatment is essential for plague and can be life-saving. The primary treatment is antibiotics, with drugs such as streptomycin, gentamicin, doxycycline, or ciprofloxacin being effective. Supportive care for severe infections, including intravenous fluids, oxygen, and respiratory support, may also be necessary.

Prevention

Preventive measures include reducing rodent habitats around homes, storing food supplies in rodent-proof containers, and using flea control products on pets. In areas where plague is common, wearing long pants and using insect repellent on skin and clothing can help prevent flea bites. Vaccines are under development but are not yet available for general use.

Epidemiology

Plague is found on all continents except Oceania but is most prevalent in Africa, Asia, and the Americas. Modern outbreaks are typically rural and occur in small clusters. The World Health Organization reports 1,000 to 2,000 cases each year, but the true number is likely higher due to underreporting.

History

Plague has a long history as a human pathogen, with pandemics occurring throughout recorded history. The most notable pandemic was the Black Death of the 14th century. The disease's impact on society has been profound, influencing population dynamics, economic conditions, and cultural practices.

See Also

• Epidemiology
• Infectious disease
• Yersinia pestis
• Black Death

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  Yersinia pestis under a fluorescent microscope
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  Buboes caused by the plague
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  Types of plague
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  Xenopsylla cheopis, the oriental rat flea
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  Ulceration of flea bite caused by Yersinia pestis
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  World distribution of plague in 1998