Flu cases in summer season show a sharp increase, NICD warns

There has been a steady increase in the number of influenza cases from the week starting August 23, with a sharp increase in the week beginning November 1 in a number of surveillance sites, the National Institute for Communicable Diseases (NICD) said on Wednesday.

In addition, private laboratories have reported an increase in influenza case detections and the NICD has received reports of clusters of cases in schools and workplaces.

The NICD said influenza A(H3N2), influenza A(H1N1)pdm09 and influenza B are seasonal virus strains that are common in human populations.

The NICD said as of the week ending November 7, the total number of influenza cases detected by the syndromic sentinel surveillance programmes conducted by the NICD has increased from 68 in week 34 (week starting August 1) to 226 at the beginning of November.

It said the increase in case numbers has been identified in all five provinces where surveillance is conducted.

To date, the most commonly detected subtype and lineage is influenza B Victoria (87 cases out of 226, 38.5%) followed by influenza A (H1N1) pdm09 (53/226, 23.5%) and influenza A (H3N2) (24/226, 10.6%).

The NICD said even though the detection rates for influenza in its surveillance programme exceeded previous seasonal thresholds, absolute numbers remained relatively low compared with previous years, possibly as a result of reduced health-seeking behaviour following the SARS-CoV-2 pandemic.

“Though most people with influenza will present with mild illness, influenza may cause severe illness which may require hospitalisation or cause death, especially in individuals who are at risk of severe influenza complications,” said Dr Sibongile Walaza, medical epidemiologist at the Centre for Respiratory Diseases and Meningitis (CRDM) at the NICD.

The NICD said groups at an increased risk of severe complications of influenza include pregnant women, HIV-infected individuals, those with chronic illnesses or conditions such as diabetes, lung disease, tuberculosis, heart disease, renal disease and obesity, those 65 years and older and children under the age of two years.

It said these groups should be encouraged to seek medical help early.

“The increase in influenza in the summer, which is not the typical time for the influenza season, is likely the result of relaxation of non-pharmaceutical interventions to control Covid-19, combined with an immunity gap due to influenza not circulating for two years (2020 and 2021) in SA (as a result of these interventions),” said Prof Cheryl Cohen, head of the CRDM.

Cohen said the influenza vaccine remained the primary means for preventing seasonal infection and should ideally be administered before the flu season from March to April.

The NICD said because of recent reductions in transmission, influenza may not circulate in the traditional seasonal period.

To prevent contracting or spreading flu, the NICD advised people to avoid close contact with sick people, stay home when you are ill and cover their mouth and nose when coughing or sneezing.

People should also clean their hands regularly, avoid touching their mouths, eyes and noses and clean and disinfect common places.

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