The following is a summary of “Assessing the Impact of SARS-CoV-2 on Influenza-Like Illness Surveillance Trends in the Community during the 2023/2024 Winter in England,” published in the November 2024 issue of Infectious Disease by Mellor et al.
Researchers conducted a retrospective study to explore the individuals with SARS-CoV-2 positive, influenced surveillance trends for influenza-like illness criteria set by World Health Organisation (WHO), Centre for Disease Control (CDC), and European Centre for Disease Control (ECDC).
They utilized data from the Winter COVID-19 Infection Study in England to model the prevalence of various influenza-like illness definitions using multilevel regression and poststratification, incorporating age, spatial stratifications, and temporal smoothing. The trends over time were compared in the individuals with SARS-CoV-2 positive and negative to analyze differences in influenza-like illness trends. Symptom presentation was also compared between positive and negative SARS-CoV-2 cases.
The results showed that SARS-CoV-2 symptom profiles overlap with influenza-like illness case definitions, particularly for “cough” and “fever,” leading to frequent misclassification in individuals with SARS-CoV-2 positive as influenza-like illness cases. The trend of SARS-CoV-2 positive cases significantly contributed to the modeled ILI trend, causing an earlier perceived peak in prevalence. The ECDC symptom definition was most affected by the patients with SARS-CoV-2 positive.
Investigators concluded that SARS-CoV-2 significantly impacts influenza-like-illness surveillance trends, making it a less reliable proxy for influenza activity alone.
Source: ijidonline.com/article/S1201-9712(24)00383-7/fulltext
