Coronavirus disease (COVID-19) technical guidance by WHO Household transmission investigation protocol | Page 11

2.2.2 Household contact definitions
The definition and further classification of household contacts are described in Box 2.
Box 2. Household contacts definition and classification
Household definition
For the purpose of this investigation, a household is defined as a group of people (two or more)
living in the same residence.
In practice, the technical definition may vary, due to social, political and cultural practices.
Definitions of a household that may be used include, but are not limited to:


two or more people living together in a domestic residence (residential institutions, such as
boarding schools, dormitories, hostels or prisons will be excluded); and
a dwelling or group of dwellings with a shared kitchen or common opening onto a shared
household space.
Household contact definition
For the purpose of this investigation, a household contact is defined as any person who has
resided in the same household (or other closed setting) as a confirmed COVID-19 case.
COMMENT: For the purposes of comparability between investigations, it is important that whichever
definition of a household contact is used is well detailed in any reporting on the investigation.
2.3 Duration
The investigation can continue for as long as is determined feasible by the country implementing the
investigation. However, ideally, enrolled household contacts will complete four home visits, to
include the enrolment visit (Day 1) and three follow-up visits within 28 days of enrolment. Specimens
and information on risk factors and symptoms will be collected from primary cases and from each
of his/her household contacts. The duration of follow-up may vary depending on further secondary
objectives.
Study enrolment could be extended as far as desired; however, the most valuable period for using
data for targeted public health action is in the early phases of the epidemic (first 2–3 months).
2.4 Data collection
2.4.1 Summary
Information on primary cases and their close contacts should be sought through a combination of
face-to-face or telephone interviews of the case (or family members if the case is too ill to be
interviewed) and household members, self-reporting, interview of health workers and/or review of
medical records where required.
Investigation questionnaires can be found in Appendix A of this document. These forms are not
exhaustive but outline the data collection required for insight into the epidemiology of COVID-19
and may be updated further. They will still need to be adapted based on the local setting and
outbreak characteristics.
-11-