Screening

Management of contacts

Definition of a contact

  • The World Health Organization (WHO) defines a contact as a person who has experienced any one of the following exposures to a probable or confirmed case:[727]

    • Face-to-face contact with a probable or confirmed case within 1 metre (3 feet) and for at least 15 minutes

    • Direct physical contact with a probable or confirmed case

    • Direct care for a patient with probable or confirmed COVID-19 without using recommended personal protective equipment

    • Other situations as determined by local health authorities based on local risk assessments.

  • Exposures must have occurred during the infectious period of the case, defined as follows:[727]

    • Exposure to a symptomatic case: 2 days before and 10 days after symptom onset of the case, plus 3 days without symptoms or 3 days with improving symptoms, for a minimum period of 13 days after symptoms onset

    • Exposure to an asymptomatic case: 2 days before and 10 days after the date on which the sample that led to confirmation was taken.

  • The US Centers for Disease Control and Prevention (CDC) defines a close contact as someone who has been within 2 metres (6 feet) of an infected person for at least 15 minutes over a 24-hour period, beginning 2 days before symptom onset (or 2 days before testing in asymptomatic patients).[127]

  • Consult your local public health authority for more information as definitions may vary.

Quarantine periods for contacts

  • The WHO recommends the following.[727]

    • Contacts who have been vaccinated (competing the primary series or with a booster dose) or previously infected in the last 90 days do not need to quarantine. However, if the contact develops symptoms within 14 days after their last exposure to a case, appropriate testing needs to be performed as soon as possible (quarantine is recommended while awaiting the test result).

    • Contacts at high risk (e.g., older age, multiple comorbidities, immunocompromised, pregnant, working in high-risk setting) and those living in high-risk settings who have not completed a primary series or received a booster vaccine dose, or who have not reported a previous infection in the last 90 days, should quarantine for 10 days. Quarantine can be shortened to 5 days if the contact tests negative on day 5 and presents no symptoms.

    • Quarantine periods of 14 days may be recommended if a new variant of concern or other priority situation emerges.

  • In the UK, contacts are no longer required to self-isolate. However, it is recommended that they avoid contact with anyone who is at higher risk of severe disease (despite vaccination), limit close contact with people outside their household (especially in crowded, enclosed, or poorly ventilated spaces), and wear a well-fitting face covering if they do need to have close contact with others.[728]

  • In the US, contacts are no longer required to self-isolate, regardless of vaccination status. However, the CDC recommends that contacts wear a high-quality mask any time they are around others inside the home or indoors in public for 10 full days, and get tested on day 6. Contacts should isolate immediately if they test positive or develop symptoms.[729]

  • Consult your local public health authority for more information as definitions may vary.

Screening of asymptomatic populations

Widespread screening of asymptomatic people is not recommended in most countries.

  • The WHO does not currently recommend widespread screening of asymptomatic individuals due to the significant costs associated with it and the lack of data on its operational effectiveness. Testing of asymptomatic individuals is currently recommended only for specific groups including contacts of confirmed or probable cases and frequently exposed groups such as healthcare workers and long-term care facility workers.[547]

  • In the US, the CDC no longer recommends screening testing of asymptomatic people without known exposures in most community settings.[730]

  • Consult your local public health authority for more information as recommendations may vary.

Drive-through screening centres

Drive-through screening centres have been set up in some countries for safer and more efficient screening. The testee does not leave their car throughout the entire process, which includes registration and questionnaire, examination, specimen collection, and instructions on what to do after. This method has the advantage of increased testing capacity and prevention of cross-infection between testees in the waiting space.[731]

Temperature screening

There is little scientific evidence to support temperature screening with thermal cameras or temperature screening products (e.g., non-contact infrared thermometers) as a reliable method for the detection of COVID-19 or any other febrile illness, especially if used as the main method of testing.[732][733][734]

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