Assignment task:
You have just started working at a health department as a public health project officer when your supervisor asks you to investigate an apparent rise in deaths caused by extensive bleeding among patients in a local hospital in Trobetown. Trobetown is a fictional picturesque harbour town of 60 000 people located in the north-western region of Australia. The city has schools, a large shopping centre and one public hospital. Most people in town work in the tourism industry. When you contact Trobetown hospital, you are told that the doctors suspect the deaths are caused by Ebola virus disease (EVD).The assembled information indicates that most patients with the suspected disease either live in a small apartment complex in town or work in the hospital. You call all apartment residents and interview hospital staff for further disease information. You also contact all general practitioners in town to inform them about the outbreak and to ask if they have seen any potential EVD cases in the last month. You find out the following:Three members belonging to one family residing in the apartment complex have been hospitalised. Before they became ill, they were visited by a family member who had travelled from Central Africa by plane. This man arrived in Trobetown on 2 June and became ill one day later.
Another 12 people in the apartment block reported being affected with similar symptoms without requiring hospitalisation.
Among the 10 hospitalised and five deceased suspected cases, there are two nurses, one doctor and one cleaner. All worked in the rooms where the patients were treated.
No other suspicious cases were reported by the general practitioners.
The lab results have come back from the laboratory in the capital city. It is confirmed that the disease is indeed Ebola. Before you continue with developing your working hypothesis regarding the source of the outbreak, modes of transmission and the population most at risk for EDV, you will need to characterise the epidemic with the use of a case definition.
What exactly is a case definition in an outbreak investigation and on what criteria is the case definition based?