Plague

Last updated: 06 September 2004

Reason for surveillance

• To identify cases, and so prevent further spread.

Case definition

A confirmed case requires laboratory definitive evidence only.

Laboratory evidence
Isolation of Yersinia pestis.

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

Notification criteria and procedure

Plague is to be notified by:
• Hospital CEOs on clinical diagnosis (ideal reporting by telephone immediately on diagnosis)
• Laboratories on confirmation (ideal reporting by telephone immediately on diagnosis).

Only confirmed cases should be entered onto NDD.

Note that plague is subject to the Commonwealth Quarantine Act (1908).

The disease

Infectious agent
The bacillus Yersinia pestis.

Mode of transmission
In countries where it is endemic (not Australia) plague is transmitted mainly from rodents (or occasionally other animals such as cats or foxes) to humans by the bite of an infected flea or by handling tissues of infected animals. Human-to-human transmission can occur by droplet infection from coughing cases with plague pneumonia or pharyngitis. There is a theoretical concern that plague could be transmitted deliberately via the airborne route, e.g., for the purposes of terrorism.

Timeline
The typical incubation period is 1 to 7 days, but shorter (1 to 4 days) for primary pneumonic plague.

Bubonic plague is communicable as long as fleas remain infective. It is not usually transmitted from person to person unless there is contact with pus from suppurating buboes.

Pneumonic plague can be highly communicable via respiratory droplets.

Clinical presentation
The usual clinical presentation is bubonic plague, which presents as a sudden onset of fever and chills, with enlarged lymph nodes (buboes), which may suppurate. The inguinal nodes are most commonly affected; less commonly the axillary and cervical nodes are affected. Bacteraemia can result in spread to a range of organs including the meninges and the lungs, where it causes a rapidly progressing pneumonia. Primary respiratory infection resulting from exposure to a patient with pneumonic plague or to materials that have been deliberately aerosolized would present as a pneumonia or pharyngitis. Symptoms of pneumonic plague include fever and productive cough which may produce blood stained sputum.

Managing single notifications

Response time

Investigation
Immediately on notification of a case begin follow-up investigation and notify the Communicable Diseases Branch.

Data Entry
Within 1 working day of notification enter confirmed
cases on NDD.

Response Procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:
• Confirm the onset date and symptoms of the illness
• Confirm results of relevant pathology tests, or recommend the tests be done
• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview
• Seek the doctor's permission to contact the case or relevant care-giver
• Review case and contact management
• Identify the likely source of infection
• Control further spread.

Investigation and treatment
See Therapeutic Guidelines: Antibiotic.

Education
The case or relevant care giver should be informed about the nature of the infection and the mode of transmission and the reason for and duration of isolation.

Exposure investigation
For bubonic plague, identify the source of infection, such as a locations visited during any recent overseas travel. In particular ask about:
• Camping
• Hiking
• Hunting
• Contact with wild rodents or other animals or fleas.

For pneumonic plague, the possibility of the case being deliberately infected should be excluded, and expert advice sought through the Communicable Disease Branch.

Isolation and restriction
Strict isolation for pneumonic plague with precautions against airborne spread, until 3 days of treatment have been completed.

Environmental evaluation
The actual or probable source of infection must be determined and preventive measures undertaken. Treat clothes, habitation and domestic pets for fleas if a possible source of infection.

Contact Management
Identification of contacts
A person with face-to-face exposure to an infectious case of pneumonic plague, or direct exposure to suppurative discharge from a case of bubonic plague in the previous 7 days. In endemic areas overseas, contacts include persons in the same household in which infected rodents or fleas reside.

Treatment
See Therapeutic Guidelines: Antibiotic.

Education
Advise susceptible contacts (or parents/guardians) of the risk of infection and the reason for and duration of quarantine.

Isolation and restriction
Contacts may be quarantined. They may be released under quarantine surveillance for up to 1 week during which they are required to notify the public health unit if suffering from a febrile illness.