Coronavirus disease (COVID-19) technical guidance by WHO Household transmission investigation protocol | Page 24

Reproduction ratio (R)
4.
Ever-changing quantity of
the number of secondary
cases produced by a primary
case across time and space
(i.e. context-specific).
Laboratory data,
dates of contact,
symptoms in
contacts.
Form 1B: Q6
Form 2, 3, 4, 5
Symptom diary
• Not the main aim of
household transmission
studies, but if the study is
continued and
transformed into a long-
term “cohort” study, it
may be possible to
calculate this.
Reporting of findings
Any investigation of this nature should include reporting on the following information, stratified by
age, sex, and relevant time and place characteristics:
 the number of households and number of household contacts included;
 the number of laboratory-confirmed COVID-19 cases among the household contacts;
 the number of symptomatic and asymptomatic household contacts; and
 the number of household contacts with serological evidence of COVID-19 infection.
Timely dissemination of the results of this investigation is critical to understanding the transmission
of the new pandemic virus, in order to update guidance and inform national and international public
health responses and policies for infection prevention and control.
It is also important to fully document the investigation design, including the definition of households
and household contacts; the approach to ascertainment of primary cases and secondary cases; the
duration of follow-up; and the laboratory methods used to ensure that data can be pooled to
increase power in estimating epidemiological parameters.
Ideally, information would be collected in a standardized format according to the questionnaires and
tools in this generic protocol, to assist with data harmonization and comparison of results (see forms
in Appendix A).
If the data are shared by the implementing organization, with WHO or with any agency or institution
providing support for data analysis, data shared will include only the investigation identification
number and not any personally identifiable information.
5.
1.
2.
3.
4.
References
The First Few X cases and contacts (FFX) investigation protocol for coronavirus disease 2019
(COVID-19). Geneva: World Health Organization; 2020.
Protocol for assessment of potential risk factors for coronavirus disease 2019 (COVID-19)
among health workers in a health-care setting. Geneva: World Health Organization; 2020
(https://www.who.int/publications-detail/protocol-for-assessment-of-potential-risk-factors-
for-2019-novel-coronavirus-(2019-ncov)-infection-among-health-care-workers-in-a-health-
care-setting, accessed 20 February 2020).
Surface sampling of COVID-19 virus: a practical “how to” protocol for health-care and public
health professionals. Geneva: World Health Organization; 2020
(https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-
guidance/early-investigations, accessed 29 February 2020).
World Health Organization. Coronavirus disease (COVID-19) technical guidance: early
investigations (https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-
guidance/early-investigations, accessed 11 February 2020).
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