Contribution of Influenza Viruses, Other Respiratory Viruses and Viral Co-Infections to Influenza-like Illness in Older Adults

• Published in: Viruses Vol. 14; no. 4; p. 797
• Main Authors: Kaaijk, Patricia, Swaans, Niels, Nicolaie, Alina M, Bruin, Jacob P, van Boxtel, Renée A J, de Lange, Marit M A, Meijer, Adam, Sanders, Elisabeth A M, van Houten, Marianne A, Rots, Nynke Y, Luytjes, Willem, van Beek, Josine
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12.04.2022; MDPI
• Subjects: Aged; Chronic illnesses; Coinfection - epidemiology; Coronavirus; Coronaviruses; Humans; Immunization; Infant; Influenza; influenza virus infection; Influenza, Human; influenza-like illness; older adults; Older people; Orthomyxoviridae; Respiratory syncytial virus; Respiratory Syncytial Virus, Human; Respiratory Tract Infections; respiratory viruses; Rhinovirus; Vaccine efficacy; Vaccines; viral co-infections; viral interference; Virus Diseases - epidemiology; Viruses; Netherlands; older adults; viral co-infections; influenza-like illness; respiratory viruses; influenza virus infection; viral interference
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v14040797

Influenza-like illness (ILI) can be caused by a range of respiratory viruses. The present study investigates the contribution of influenza and other respiratory viruses, the occurrence of viral co-infections, and the persistence of the viruses after ILI onset in older adults. During the influenza season 2014-2015, 2366 generally healthy community-dwelling older adults (≥60 years) were enrolled in the study. Viruses were identified by multiplex ligation-dependent probe-amplification assay in naso- and oropharyngeal swabs taken during acute ILI phase, and 2 and 8 weeks later. The ILI incidence was 10.7%, which did not differ between vaccinated and unvaccinated older adults; influenza virus was the most frequently detected virus (39.4%). Other viruses with significant contribution were: rhinovirus (17.3%), seasonal coronavirus (9.8%), respiratory syncytial virus (6.7%), and human metapneumovirus (6.3%). Co-infections of influenza virus with other viruses were rare. The frequency of ILI cases in older adults in this 2014-2015 season with low vaccine effectiveness was comparable to that of the 2012-2013 season with moderate vaccine efficacy. The low rate of viral co-infections observed, especially for influenza virus, suggests that influenza virus infection reduces the risk of simultaneous infection with other viruses. Viral persistence or viral co-infections did not affect the clinical outcome of ILI.