Coronavirus disease (COVID-19) technical guidance by WHO Household transmission investigation protocol | Page 42

Duration
Start of the
investigation.
and secondarily:
 the basic reproduction
number (R 0 ) of COVID-19.
 the incubation period of
COVID-19.
 the preliminary infection and
disease-severity ratios (e.g.
case-hospitalization and
case-fatality ratios).
At a minimum, enrolled cases and close
contacts will complete data and
specimen collection at enrolment (Day 1)
and 14–21 days later, with two home
visits.
To be initiated in the first days after the
arrival in Country X of a confirmed case
of COVID-19.
FFX is the primary protocol to be initiated
in the case of a COVID-19 outbreak, upon
identification of the initial
laboratory-confirmed cases of COVID-19
virus in Country X in the early epidemic
phases.



high-risk population subgroups
the secondary infection rate and
secondary clinical attack rate of
COVID-19 infection among
household contacts.
patterns of health-care seeking.
Households will complete a minimum
of four home visits within 28 days of
enrolment/follow-up.
Enrolment could be extended as far as
desired; however, the most valuable
period in order to use data for
targeted public health action is in the
early phases of the epidemic
(first 2–3 months).
Ideally to be initiated before
widespread community transmission
occurs: as early as possible after the
first cases of COVID-19 infection are
confirmed and at least within the first
2–3 months after identification of
initial cases.
This should be followed by subsequent
tracing of household contacts of early
laboratory-confirmed cases of
COVID-19 in Country X in the early
epidemic phases.
-42-
Health workers and health-care facilities will
complete a minimum of two site visits within
21 days of enrolment/follow-up.
To be initiated with the first identification of a
laboratory-confirmed case of COVID-19 in a
health-care setting.
This should be followed by subsequent tracing of
health worker contacts of early laboratory-
confirmed cases of COVID-19 in Country X in the
early epidemic/pandemic phases.