Coronavirus disease (COVID-19) technical guidance by WHO Household transmission investigation protocol | Page 10

Other relevant inclusion/exclusion criteria for consideration by countries:
 Households could be excluded (or not, if it is possible to tease out the transmission dynamics) if:
o the date of symptom onset of COVID-19 is the same for more than one family member
(co-primary cases); or
o a household contact is symptomatic at the initial home visit on Day 1 (so identified as
a possible case), as it will increase the complexity of analyses of transmission dynamics.
 Hospitalized cases and their contacts may be excluded from this study, as they have been
removed from the household and therefore the level of exposure of household contacts is
unclear. Hospitalized individuals may only represent a small subset of individuals in the
community and are likely to be picked up in other clinical studies.
 Every effort should be made to include all identified household contacts of cases of
laboratory-confirmed COVID-19.
For the purpose of this investigation, the primary case will be identified through the national or other
relevant international surveillance system.
2.2.1 Case definitions
Case definitions for COVID-19 reporting are available on the WHO website (12), although they are
subject to further updates as more information becomes available. For the purpose of this protocol,
the generic case definitions for COVID-19 are proposed in Box 1.
Box 1. Interim case definitions for the purpose of the FFX protocol
Suspected case
A . A patient with severe acute respiratory infection (fever, cough and requiring admission to
hospital), AND with no other etiology that fully explains the clinical presentation;
OR
B . A patient with any acute respiratory illness AND at least one of the following during the 14 days
prior to symptom onset:
 contact with a confirmed or probable case of COVID-19 infection, OR
 worked in or attended a health-care facility where patients with confirmed or
probable COVID-19 were being treated.
Probable case
A suspected case for whom testing for COVID-19 is inconclusive or who tested positive using a
pan-coronavirus assay, and without laboratory evidence of other respiratory pathogens.
Confirmed case
A person with laboratory confirmation of COVID-19 infection, irrespective of clinical signs and
symptoms.
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