Avian Flu Diary: The Lancet: SARS-CoV-2 Co-infection With Influenza Viruses, RSV, or Adenoviruses

#16,658

The great hope with the SARS-CoV-2 virus is that people will acquire enough immunity - or the virus will attenuate sufficiently - to allow it to become part of the panoply of seasonal respiratory viruses and no longer act like a `pandemic' virus.

Whether that happens this year, or next, it will result in COVID co-circulating with influenza, RSV, Adenoviruses and other `seasonal' viruses. And that will increase the chances of seeing coinfections.

While we've seen some early studies suggesting that coinfection may be linked to higher mortality (see IDCases: Co-infection With SARS-CoV-2), the lack of influenza activity during the first 18 months of the pandemic has limited the available data.

In 2020, a PHE Study: Co-Infection With COVID-19 & Seasonal Influenza, found that coinfection more than doubled the risk of death over having COVID alone.
We've also seen several animal studies (see here, here, and here) that found higher pathogenicity in coinfected mice and ferrets.

On Friday The Lancet published a correspondence from researchers who have conducted the largest study to date on COVID coinfections, one which included data from over from over 212,000 adults hospitalized for SARS-CoV-2 infection in the UK (between Feb 6, 2020, and Dec 8, 2021).

Of these, tests for viral coinfections were done on 6965 patients, 583 (8.4%) of which tested positive; 227 had influenza viruses, 220 had RSV, and 136 had adenoviruses.

They reported:

Co-infection with influenza viruses was associated with increased odds of receiving invasive mechanical ventilation compared with SARS-CoV-2 monoinfection (table). SARS-CoV-2 co-infections with influenza viruses and adenoviruses were each significantly associated with increased odds of death.

Drilling down into the data, coinfection with influenza (among hospitalized patients) was linked to a 4-fold increased likelihood of requiring mechanical ventilation, and a roughly doubled risk for death.

While the impact was most pronounced with influenza, they also noted a smaller increase in mortality for patients coinfected with COVID-Adenovirus.

The link, and some excerpts from the letter follow. I'll return with a brief postscript after the break.

SARS-CoV-2 co-infection with influenza viruses, respiratory syncytial virus, or adenoviruses
Maaike C Swets, Clark D Russell, Ewen M Harrison, Annemarie B Docherty, Nazir Lone, Michelle Girvan et al. Show all authors
Open Access Published:March 25, 2022 DOI:https://doi.org/10.1016/S0140-6736(22)00383-X
PDF [70 KB]

Measures to reduce transmission of SARS-CoV-2 have also been effective in reducing the transmission of other endemic respiratory viruses.1, 2 As many countries decrease the use of such measures, 2 we expect that SARS-CoV-2 will circulate with other respiratory viruses, increasing the probability of co-infections.1,3 The clinical outcome of respiratory viral co-infections with SARS-CoV-2 is unknown.

We examined clinical outcomes of co-infection with influenza viruses, respiratory syncytial virus, or adenoviruses in 212 466 adults with SARS-CoV-2 infection who were admitted to hospital in the UK between Feb 6, 2020, and Dec 8, 2021, using the International Severe Acute Respiratory and Emerging Infection Consortium–WHO Clinical Characterisation Protocol.4

Details on patient recruitment, inclusion criteria, testing, and statistical analyses are included in the appendix (pp 2–3). Ethical approval was given by the South Central-Oxford C Research Ethics Committee in England (13/SC/0149), the Scotland A Research Ethics Committee (20/SS/0028), and the WHO Ethics Review Committee (RPC571 and RPC572, April, 2013).

Tests for respiratory viral co-infections were recorded for 6965 patients with SARS-CoV-2. Viral co-infection was detected in 583 (8·4%) patients: 227 patients had influenza viruses, 220 patients had respiratory syncytial virus, and 136 patients had adenoviruses. Co-infection with influenza viruses was associated with increased odds of receiving invasive mechanical ventilation compared with SARS-CoV-2 monoinfection (table). SARS-CoV-2 co-infections with influenza viruses and adenoviruses were each significantly associated with increased odds of death.

(SNIP)

As public health restrictions are lifted, respiratory virus co-infections are more likely to occur during future winters. The marked increase in risk among patients with co-infection has several implications for policy. First, our results provide further support for vaccination against both SARS-CoV-2 and influenza viruses. Second, they suggest that testing for influenza viruses is important in hospital inpatients with COVID-19 to identify patients at risk and a cohort of patients who might have different responses to immunomodulatory and antiviral therapy.

(Continue . . . .)

Based on the data collection dates (cut off Dec 8, 2021) very few of these cases are likely to have had Omicron, and so we'll need to see more data to know if these trends continue with our latest (and future) variants.

Some additional past blogs on COVID-Flu coinfections may be found at: