< Tests

Should I get tested before seeing friends and family?

Text updated on 2020-12-21


Yes, if you have had any high-risk interactions in the past two weeks and if tests are available in your area. If your result is negative, stay vigilant because you can be contagious 24 hours after a negative test and there are false negatives.

During the winter period, large-scale gatherings of family or friends during the chinese new year in China, Thanksgiving in the United States or the 2020 holiday season have been discouraged to limit the spread of the epidemic. The coronavirus spreads efficiently during indoor meetings and meals, where people will have prolonged contact without masks and where distances between individuals are greatly reduced. See the question What is close contact? It is therefore critical that everyone tries to keep coronavirus transmission to a minimum over the holidays. In many countries, it is advisable to get tested before you meet with others. Is it useful to do a COVID-19 test before Christmas?

If you have had no contact with risk of transmission in the previous 14 days (no masked interaction, no children, etc.), you probably don't need to go for testing. Our Questionnaire to evaluate your risk of contamination during the last 2 weeks..

If you have had one or more contacts with risk of transmission during the 14 days, you may decide to go for testing if tests are available in your country. 

If your test is negative, please note that this is not a 100% guarantee that you are not infected with coronavirus or contagious. You should not let your guard down for three reasons:

  1. There are false negatives, i.e., individuals who test negative while infected. The rate of false negatives varies between tests. In France, the High Authority of Health has validated tests with less than 20% false negatives, i.e., in 2 cases out of 10, the test is negative even though those persons are infected with the coronavirus, and probably contagious.
  2. You can become contagious 24 hours after your swab comes back negative. A negative result means that you will not release the virus within 24 hours of providing the sample. However, it is possible to be positive the day after a negative test. A 13-year-old girl had an antigen test before she saw her parents again and the test was negative. The next day, she had a stuffed nose and still decided to attend a family gathering of 15 people that lasted several days and infected 12 people. 
  3. In the case of RT-PCR tests, there is a long delay in obtaining test results. It can be 1 to 3 days, or even 5 to 7 days if many people are going to be tested at the same time, which is possible if everyone decides to be tested before Christmas or New Year's Day. Keep in mind that the test result tells us the status (positive or negative) of the day we got tested and not the day we get the result. For example, a test done on Wednesday for a result obtained on Friday indicates the status you had on Wednesday but not the status on Friday.

If your result is positive, it is almost certain that you have coronavirus because globally, COVID tests are very specific, i.e., there are few people who test positive when in fact they are not infected with coronavirus (countries do not wish to inflate their positive case numbers with non-specific tests). See the question False Positives, False Negatives, Sensitivity, Specificity of COVID Tests : What are we talking about?(https://www.adioscorona.org/questions-reponses/2020-12-04-test-covid-sensitivity-specificity-false-negative-true-positive-reliability.html)

In the event of a positive test:

If your test is negative but you still think you may be at risk of the contagion because the family reunion takes place more than a day after the sample is given, we advise you:

In conclusion, the test is not perfect. The ideal way to prevent the spread of the virus is to avoid as much as possible potentially contagious situations in the 1-2 weeks before and after the party. It is also important to reduce the number of guests and not to meet several groups at the same time (mother's and father's family, for example).


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Sources

Analysis of an outbreak showing that large family gatherings can be events where transmission of the SARS-CoV-2 coronavirus is important.

Ghinai, I., Woods, S., Ritger, K. A., McPherson, T. D., Black, S. R., Sparrow, L., ... & Arwady, M. A. (2020). Community transmission of SARS-CoV-2 at two family gatherings-Chicago, Illinois, February-March 2020.

Several people from the same family were contaminated after two family reunion dinners.

Ye, F., Xu, S., Rong, Z., Xu, R., Liu, X., Deng, P., ... & Xu, X. (2020). Delivery of infection from asymptomatic carriers of COVID-19 in a familial cluster. International Journal of Infectious Diseases.

Article discussing the effect of the 2020 Thanksgiving reunions on the number of COVID-19 cases in the United States.

Aldhous, P. (2020). The US Didn't See A Major Additional COVID-19 Thanksgiving Surge. Christmas Will Be A Bigger Challenge. BuzzFeed. 19 Dec 2020. Last Accessed 21 Dec 2020.

At the end of September 2020, the French High Authority for Health issued an opinion in favour of the use of antigenic tests on nasopharyngeal swabs only in people who present symptoms of COVID-19 (fever, dry cough, loss of smell or taste, etc.) if the test performance is: minimum sensitivity greater than 80% and minimum specificity greater than 99%.

Opinion of the High Authority for Health of October 9, 2020.

A few false positive RT-PCR tests have been reported. They are linked to frequent contaminations with an amplicon containing the virus.

Wernike, K., Keller, M., Conraths, F. J., Mettenleiter, T. C., Groschup, M. H., & Beer, M. (2020). Pitfalls in SARS-CoV-2 PCR diagnostics. bioRxiv.

Daily RT-qPCR tests were conducted on many individuals during the 2019-20 National Basketball Association (NBA) season. Viral load was measured daily in 46 people who developed COVID-19 during the sporting events. People who tested negative one day turned out to be positive the next.

Kissler, S. M., Fauver, J. R., Mack, C., Olesen, S. W., Tai, C., Shiue, K. Y., ... & Wohlgemuth, J. (2020). SARS-CoV-2 viral dynamics in acute infections. medRxiv.

A 13-year-old girl took an antigen test before she saw her parents again and the test was negative. The next day, she had a stuffed nose and still decided to attend a family gathering of 15 people that lasted several days and infected 12 people. Six other guests came to the family reunion for several hours without masks but stayed outside and did not develop any symptoms, and the four who later tested were negative.

Schwartz, N. G., Moorman, A. C., Makaretz, A., Chang, K. T., Chu, V. T., Szablewski, C. M., ... & Drobeniuc, J. (2020). Adolescent with COVID-19 as the Source of an Outbreak at a 3-Week Family Gathering-Four States, June-July 2020. Morbidity and Mortality Weekly Report, 69(40), 1457.

Further reading

Why are gatherings not recommended during the outbreak of COVID-19 ?

Can a person without symptoms infect others?

What is the baseline test to find out if I am infected with SARS-CoV-2?

What sample to test for COVID-19: nasopharyngeal or buccal?

How many days after contact should I wait for a COVID test?

False positives, false negatives, sensitivity, specificity of COVID tests: what are we talking about?

We are planning a family reunion for the holidays: how to do it?

How to organize a meal at home without risk to the guests?