COVID-19: Where Are the Other Seasonal Respiratory Viruses?

Dawn O'Shea

November 27, 2020

The emergence of SARS-CoV-2 was associated with substantial reductions in the circulation of seasonal respiratory viruses and large differences in the characteristics of viral-associated disease, reports a study published in the  Journal of Infection.

The researchers examined data from hospitalised adults who had multiplex polymerase chain reaction (PCR) testing for respiratory viruses over several seasons in Hampshire, UK. Respiratory virus detection during the first epidemic peak of SARS-CoV-2 was compared with detection during the same time across previous years.

A total of 856 patients had multiplex PCR for respiratory viruses between March and May over five years. Before 2020, a non-SARS-CoV-2 virus was detected in 54 per cent of patients (202/371) compared to 4.1 per cent (20/485) in 2020 (P<.0001). SARS-CoV-2 was rarely co-detected with other respiratory viruses.

Furthermore, SARS-CoV-2 was infrequently associated with exacerbations of chronic obstructive pulmonary disease or asthma compared to other viruses (1.0% vs 37%; P<.0001).

Almost all patients with any virus detected were given antibiotic therapy, despite the lack of evidence for their utility use in viral infection. This highlights an unmet need for better diagnostic tests which allow differentiation between viral and bacterial infections.

The authors describe the low levels of expected viruses as “remarkable” and said the explanation for this is likely to be multifactorial. “Seasonal respiratory viruses typically have a shorter incubation period than SARS-CoV-2, therefore transmission of these viruses may have been impacted earlier by the effects of social distancing measures and the nationwide lockdown that was introduced on 23rd March 2020. Indeed, it seems highly likely that the measures introduced to reduce transmission of SARS-CoV-2 are the main reason for the significant reduction in the spread of other respiratory viruses. Other transmissible diseases, such as measles, have reported a similar decline.”

It has also been theorised that previous epidemic influenza viruses have been slowed by interaction with existing viral infections. The authors say the low rate of co-infection seen here raises the possibility that viral interference may have played a role in the reduced prevalence of other respiratory viruses.

Poole S, Brendish NJ, Clark TW. SARS-CoV-2 has displaced other seasonal respiratory viruses: Results from a prospective cohort study. J Infect. 2020 Nov 15 [Epub ahead of print]. doi: 10.1016/j.jinf.2020.11.010. PMID: 33207254 View full text

This article originally appeared on Univadis, part of the Medscape Professional Network.

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