2018 Influenza Season Update

The annual influenza season, which started in the first week of May 2018 is ongoing. To date, the majority 249/253 (98%) of influenza positive samples for this season, detected by the Viral Watch surveillance programme, have been identified as influenza A(H1N1)pdm09 (Figure1). Similarly, all influenza detections in the public health sector influenza surveillance programmes (pneumonia surveillance and influenza-like illness) have been identified as A(H1N1)pdm09.

This strain emerged globally in 2009 during the pandemic when it was referred to as “Swine flu”, and since then has been part of the seasonal circulating influenza strains. Patients infected with this strain should be treated like any other seasonal influenza case. There is no requirement to report or notify individual cases of this strain of influenza.

Influenza is usually an uncomplicated illness, which is characterised by sudden onset of constitutional and respiratory symptoms such as fever, myalgia, cough, sore throat, rhinitis and headache. Influenza typically resolves in 3-7 days in the majority of individuals. In a proportion of patients, influenza may be associated with more severe illness or complications, these complications include viral pneumonia, secondary bacterial or viral infections (including pneumonia, sinusitis and otitis media), and exacerbations of underlying illnesses (e.g. pulmonary and cardiac illness). Every year there are cases of severe and complicated influenza in otherwise healthy persons, however, these are rare events.

Influenza vaccination remains the most effective measure to prevent illness and possibly fatal outcomes. Individuals at risk of severe influenza illness and complications include among others pregnant women, those with pre-existing chronic illnesses (e.g. diabetes, asthma, HIV) or other risk factors and the very young and elderly. Vaccines should be given sufficiently early to provide protection for the influenza season, though it is never too late to vaccinate.

Oseltamivir (Tamflu®) may decrease the duration and severity of influenza illness in patients who are very ill with influenza and it should be considered for those patients who are hospitalised with severe influenza illness especially those at risk of serious influenza complications. The maximum benefit of Oseltamivir is early in infection i.e. within 48 hours of the onset of illness.

Influenza NICD recommendations for diagnosis, prevention, management and public health response, can be accessed at https://www.nicd.ac.za/wp-content/uploads/2017/03/Influenza-guidelines-rev_-23-April-2018.pdf

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