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: - - 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. 2