Outbreaks of infectious disease
Definition of an outbreak
There are many definitions of an outbreak. They include:
- >1 case, linked together in space and time, with evidence of cross-infection;
- (If background incidence is known) observed incidence > expected incidence. (True background incidence/prevalence seldom known, so this definition is not very useful.)
- Any number of cases which produces (or is likely to produce) a media reaction: if there is a lot of interest, or severe illness, or death, then this will influence the decision to call an outbreak meeting.
Increasingly the terms incident and incident team meeting are being used, as the approach to many incidents, including those involving non-infectious environmental hazard(s) (NIEH) is similar.
Response to an outbreak
Summary of response to an outbreak of communicable disease - "CCDC":
- Contingency plan
- Communication - liase and support
- Control - prevention and monitoring
Actions in response to reports of an outbreak:
- Confirm the existence of epidemic or outbreak
- Verify the diagnosis
- Formulate a preliminary hypothesis for the cause of the episode
- Undertake immediate control measures if necessary
- Identify and count cases or exposure - create a case definition. (Seek/receive information from e.g. members of the public, GPs, hospital doctors or laboratories, environmental health...)
- Investigate outbreak - outbreak control team usually led by Consultant in Communicable Disease Control if in community, and by hospital infection control team if outbreak arises in a hospital.
- Control measures as necessary (isolation of infected patients, closure of wards, restriction of staff movements between wards, surveillance of contacts, examination of all staff and patients for carriage, bacteriological specimens, survey of procedures and practice, equipment and buildings, etc.)
- Evaluate control measures (continued surveillance)
- Communicate findings: Collate outbreak data; Formal and informal reports; Publications.