Plague

Overview

Plague is a zoonotic disease caused by Yersinia pestis bacteria, usually found in small mammals and their fleas.

There are 3 clinical forms of plague: Bubonic, Septicaemic and Pneumonic plague.

Pathogen(s)

Yersinia pestis bacteria

Transmission

Plague can be transmitted from rats by flea bites, by handling infected animal tissues, or airborne by aerosol from animals or humans with pneumonic plague.

Incubation period: 1 to 7 days

Infectious period: Throughout duration of illness or until 48 hours after receiving effective antibiotic therapy.

Clinical features

Plague should be suspected in anyone with fever and painful lymphadenopathy who has been to an endemic country.

There are three principal clinical presentations:

• Bubonic plague: Initial fever, headache, myalgia followed by painful acute regional lymphadenopathy (pathognomonic bubo), typically involving the inguinal, axillary or cervical regions. If left untreated, rapid progression to septicaemia and secondary plague pneumonia occurs (fatality rate is between 50%–60%).

• Septicaemic plague: Occurs when Y.pestis invades the bloodstream. It can follow bubonic plague or occur without detectable lymphadenopathy (primary septicaemic plague). Complications include septic shock, disseminated intravascular coagulation, meningitis, and multiorgan failure.

• Pneumonic plague: It is the least common but most dangerous and fatal form of the disease. It can develop as a complication of septicaemic plague or be acquired directly by inhalation of aerosols from a human or animal with pneumonic plague. The signs include severe pneumonia, fever, dyspnoea, and often haemoptysis. Patients who do not receive treatment within 18 hours of onset of respiratory symptoms are unlikely to survive.

Risk factors

Risk factors include:

• Persons who live in areas with poor rodent sanitation practices

• Hunters, trappers, trekkers, veterinary staff, and farmers operating during or following an epizootic are at increased risk

• Travel history to and rodent exposure in plague-affected countries

Diagnosis

Plague is diagnosed when a laboratory test detects Y.pestis bacteria in a person’s blood, bubo aspirate, respiratory specimens or necropsy material.

Treatment and management

Antibiotic therapy is highly effective if used within hours of presentation.

Precaution, Prevention, and Control

• Patients with uncomplicated infection present no health hazards to others when promptly treated

• Cases with cough and other signs of pneumonia must be placed in strict respiratory isolation for at least 48 hours after the institution of antibiotic therapy or until the sputum culture is negative

• Standard precautions should be applied when handling suspect or confirmed plague patients and their body fluids and tissues. Bubo aspirate and blood must be handled with gloves and aerosolisation of these materials should be avoided

• In the event of death, proper disposal of the body must be observed.

• Anti-flea and rodent control measures should be implemented if they are the likely source of infection

• Chemoprophylaxis should be offered to persons exposed to bites of wild rodent fleas during an outbreak or to tissues/fluids of a plague-infected animal, and to persons travelling to highly endemic area for short duration

• No licensed plague vaccine is currently available

Notification

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• On clinical suspicion or laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• Immediately. No later than 24 hours from the time of diagnosis.