Other respiratory viruses may reduce SARS-CoV-2 co-detection, but the effect weakened without symptom-based testing

Design

Individual participant data meta-analysis of ten cohort studies, 2020 to 2024

Population

Six cohorts (1,023 participants) with testing regardless of symptoms; five symptomatic cohorts (1,715 participants)

Primary outcome

Odds of SARS-CoV-2 detection in samples positive for another respiratory virus

Effect

Unselected testing OR 0.72 (95% CI 0.40 to 1.25); symptomatic testing OR 0.16 (95% CI 0.10 to 0.25)

This individual participant data meta-analysis pooled ten cohort studies conducted between 2020 and 2024. Respiratory samples were tested by PCR for several viruses including SARS-CoV-2. The primary analysis used samples collected regardless of symptoms (six cohorts, 1,023 participants, 2,465 samples, 8.3% SARS-CoV-2 positive).

In that analysis, co-detection with another virus occurred less often than expected if viruses did not interfere with one another, but the estimate was not statistically significant (OR 0.72, 95% CI 0.40 to 1.25). In symptom-based testing (five cohorts, 1,715 participants, 2,088 samples, 24.2% positive) the odds ratio was 0.16 (95% CI 0.10 to 0.25).

The large gap suggests that testing only symptomatic people exaggerates the association, since a person with one virus is less likely to be tested for another. It supports the idea of viral interference, but modestly. For clinicians, a positive test for one respiratory virus does not exclude a second.

• In samples taken regardless of symptoms, co-detection odds were 0.72 (95% CI 0.40 to 1.25), not significant.
• In symptom-driven testing the odds ratio was 0.16, which is likely inflated by selection.
• A positive result for one respiratory virus does not exclude another.
• Testing practice affects the apparent interaction between viruses.
• Treat this as epidemiology, with no effect on individual patient management.

Why it matters

It shows how much testing strategy can create an apparent biological effect.

Don't overread it

The primary estimate was not significant, so the study does not establish that viruses block one another.

The statistics, in plain English

An odds ratio of 0.72 with an interval of 0.40 to 1.25 is compatible with a moderate reduction, no effect or a small increase. The much lower 0.16 from symptomatic testing is probably distorted by who gets tested, which is why the unselected estimate is the more trustworthy one.

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