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Summer viruses on the radar

Viruses are often associated with acute respiratory infections, for example, in the summer, rhinoviruses are the most common causes of acute respiratory infections. A comprehensive review of epidemiology studies shows that they are the most frequently isolated viruses during the summer months (1). Since respiratory viruses are generally transmitted through inhalation or direct contact with respiratory aerosols or secretions, the environment (temperature, humidity, UV) plays a crucial role on their survival and transmission. This would be the case of rhinoviruses, but also respiratory non polio enteroviruses, influenza A etc.

  • Respiratory non polio enteroviruses are responsible for what are known as summer colds. In the Northern hemisphere, they thrive between June and October (2, 3). They spread in aerosols, through coughing and sneezing. Respiratory infections with enteroviruses cause mild upper respiratory symptoms, sore throats, rashes and other symptoms beyond the common cold’s typical headache, hacking cough, congestion and low fever. Summer colds often last longer and have a higher chance of recurring as compared to winter colds, mostly caused by rhinoviruses.
  • Influenza A appears to be both more prominent and more virulent in summer. Epidemiology studies under sub-tropical climates (4) show two seasonal peaks, one in winter/spring and one in summer in most years. They suggested that hot and humid conditions were associated with a higher activity of influenza.
  • Adenoviruses are responsible for many infections, including respiratory, ocular and enteric infections or pneumonia. An extensive review of recreational water-borne viral outbreaks from 1951-2006 reported adenovirus as the second leading cause of water-borne virus outbreaks, present in 24% of these outbreaks, essentially in pools (5).



  1. Monto AS. The seasonality of rhinovirus infections and its implications for clinical recognition. Clin Ther. 2002 Dec;24(12):1987-97
  2. Coughtrie AL et al., Epidemiological and ecological modelling reveal diversity in microbial population structures from a cross-sectional community swabbing study. Preprint article Jan 2017 doi:
  3. Meneghetti A. Upper Respiratory Tract Infection Medscape, 2011.
  4. Chan PK et al. Seasonal influenza activity in Hong Kong and its association with meteorological variations. J Med Virol. 2009 Oct;81(10):1797-806.
  5. Sinclair R.G., Jones E.L. and Gerba C.P. Viruses in recreational water-borne disease outbreaks: a review. Journal of Applied Microbiology 107 (2009) 1769–1780.