Coronavirus disease (COVID-19) technical guidance by WHO Laboratory testing for COVID-19 | Page 2

Laboratory testing for coronavirus disease 2019 (COVID-19) in suspected human cases
In an early study in Wuhan, the mean incubation
period for COVID-19 was 5.2 days among 425 cases,
though it varies widely between individuals
(11,12,13). Virus shedding patterns are not yet well
understood and further investigations are needed to
better understand the timing, compartmentalization
and quantity of viral shedding to inform optimal
specimen collection. Though respiratory samples
have the greatest yield, the virus can be detected in
other specimens, including stool and blood
(14,15,16). Local guidelines should be followed
regarding patient or guardian’s informed consent for
specimen collection, testing and potentially future
research.
Specimens to be collected
At minimum, respiratory material should be
collected:
-
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upper respiratory specimens:
nasopharyngeal and oropharyngeal swab
or wash in ambulatory patients
and/or lower respiratory specimens:
sputum (if produced) and/or endotracheal
aspirate or bronchoalveolar lavage in
patients with more severe respiratory
disease. (Note high risk of aerosolization;
adhere strictly to infection prevention and
control procedures).
Additional clinical specimens may be collected as
COVID-19 virus has been detected in blood and
stool, as had the coronaviruses responsible for SARS
and MERS (14,16,19-21). The duration and
frequency of shedding of COVID-19 virus in stool
and potentially in urine is unknown. In case of
patients who are deceased, consider autopsy
material including lung tissue. In surviving patients,
paired serum (acute and convalescent) can be useful
to retrospectively define cases as serological assays
become available.
3. Specimen collection and shipment
Safety procedures during specimen collection
Ensure that adequate SOPs are in use and that staff
are trained for appropriate specimen collection,
storage, packaging and transport. All specimens
collected for laboratory investigations should be
regarded as potentially infectious.
Ensure that health care workers who collect
specimens adhere rigorously to infection prevention
and control guidelines. Specific WHO interim
guidance has been published: “Infection prevention
and control during health care when novel
coronavirus (nCoV) infection is suspected, interim
guidance, January 2020” (17) and “WHO interim
guidance for laboratory biosafety related to 2019-
nCoV” (18).
Further recommendations on materials to collect,
including the testing of asymptomatic individuals,
can be found in Table 1.
Packaging and shipment of clinical specimens
Specimens for virus detection should reach the
laboratory as soon as possible after collection.
Correct handling of specimens during transportation
is essential. Specimens which can be delivered
promptly to the laboratory can be stored and shipped
at 2-8°C. When there is likely to be a delay in
specimens reaching the laboratory, the use of viral
transport medium is strongly recommended.
Specimens may be frozen to - 20°C or ideally -70°C
and shipped on dry ice if further delays are expected
(see Table 2). It is important to avoid repeated
freezing and thawing of specimens.
Box 1. Biosafety practices in the laboratory
Testing on clinical specimens from patients meeting the
suspect case definition should be performed in appropriately
equipped laboratories by staff trained in the relevant technical
and safety procedures. National guidelines on laboratory
biosafety should be followed in all circumstances. There is
still limited information on the risk posed by COVID-19, but
all procedures should be undertaken based on a risk
assessment. Specimen handling for molecular testing would
require BSL-2 or equivalent facilities. Attempts to culture the
virus require BSL-3 facilities at minimum.
Transport of specimens within national borders
should comply with applicable national regulations.
International transport of potentially COVID-19
virus containing samples should follow the UN
Model Regulations, and any other applicable
regulations depending on the mode of transport
being used. More information may be found in the
“WHO Guidance on regulations for the Transport of
For more information related to COVID-19 risk assessment,
see specific interim guidance document: ’WHO interim
guidance for laboratory biosafety related to 2019-nCoV’ (18).
Samples that are potentially infectious materials (PIM) for
polio need to be handled and stored as described in WHO
document “Guidance to minimize risks for facilities
collecting, handling or storing materials potentially infectious
for polioviruses (PIM Guidance)” (23). For general laboratory
biosafety guidelines, see the WHO Laboratory Biosafety
Manual, 3rd edition before the 4th edition is released.
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