Screening

Management of contacts

Definition

  • The World Health Organization defines a contact as a person who has experienced any one of the following exposures to a probable or confirmed case:[755]

    • 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:[755]

    • 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).[120]

  • Consult local guidance as definitions of a contact may vary depending on local public health advice.

Quarantine periods

  • The World Health Organization recommends the following.[755]

    • 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.[756]

  • In the US, the CDC recommends that contacts who are up-to-date with vaccinations do not need to quarantine unless they develop symptoms. However, they should get tested at least 5 days after their exposure even if they don’t develop symptoms (except people with confirmed COVID-19 within the past 90 days), and take precautions until day 10 (e.g., wear a mask around others, take precautions if travelling, avoid being around people who are at high risk). Contacts who are not up-to-date with their vaccinations are required to quarantine for at least 5 days, get tested at least 5 days after their exposure even if they don’t develop symptoms, and take the same precautions until day 10.[757]

  • Consult local guidance for recommended quarantine locations and timeframes as recommendations vary depending on local public health advice.

Screening of asymptomatic populations

The World Health Organization 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.[552]

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.[758]

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.[759][760][761]

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