Kovacevic A, Eggo RM, Baguelin M, et al. - There can be a distortion in SARS-CoV-2 surveillance due to the presence of the co-circulating respiratory viruses. Multiplex PCR tests can result in correction of the positivity rate, and a low number of samples is sufficient to avoid bias in SARS-CoV-2 surveillance.

• The impact of an outbreak of secondary virus on two COVID-19 surveillance indicators (testing demand and positivity) was determined by using a multi-pathogen Susceptible-Exposed-Infectious-Recovered (SEIR) transmission model formalizing co-circulation of SARS-CoV-2 and another respiratory virus.

• A strong rise in SARS-CoV-2 daily testing demand and an artificial decrease in the observed SARS-CoV-2 percent positivity was evident because of the non-SARS-CoV-2 epidemic during the outbreak.

• As per estimates, it is sufficient to perform one multiplex test for every 1,000 COVID-19 tests on symptomatic individuals for maintaining surveillance of other respiratory viruses in the population and for rectifying the observed SARS-CoV-2 percent positivity.