The 2026 influenza season started in week 11 (week starting 9 March 2026) when the influenza detection rate from the NICD inpatient pneumonia sentinel surveillance in public hospitals and in outpatients attending public clinics breached the seasonal threshold and was sustained for two consecutive weeks. This is early compared to the start of the season historically, however it is similar to what was observed in 2025, where the season started in week 13 (week starting 24 March 2025) (Figure 1A).
The 2026 RSV season also started in week 11 (week starting 9 March 2026), when the RSV detection rate in children aged <5 years from inpatient pneumonia surveillance in public hospitals exceeded the seasonal threshold and was sustained for two consecutive weeks (Figure 1B). The influenza and RSV seasons both starting in the same week is an unusual event. Clinicians should be on the alert for a potential high burden of patients with respiratory illness in medical facilities in the coming weeks.
Influenza
The 2026 season marks the earliest start to the influenza season recorded since 2010, based on pneumonia surveillance data. The A(H1N1)pdm09 subtype was the most prevalent among influenza A cases in the pneumonia surveillance programme and public clinics but influenza A(H3N2) is most prevalent in outpatient surveillance in private general practitioner practices (Figure 2). Out of 6 influenza A(H1N1)pdm09 samples sequenced to date 5 were subclade D.3.1 and one was subclade D.3.1.1. Of 11 influenza A(H3N2) samples sequenced to date all were subclade K (J2.4.1). Of 7 influenza B Victoria samples sequenced to date 6 were C.5.6 and one was C.5.1.
Respiratory syncytial virus (RSV)
Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and lower respiratory tract infections (LRTI) in young children and can lead to severe illness in infants. It is highly contagious, primarily spreading through respiratory droplets, and re-infections can occur. Over the past decade (excluding pandemic years 2020 and 2021), the RSV season typically begin in mid-February (week 7), with the onset ranging from late-January to late-February, usually preceding the influenza season. Compared to historical data (excluding the SARS-CoV-2 pandemic period), the start of the 2026 RSV season is approximately 4 weeks later than the average, but similar to 2025 when the season also started late (Figure 1B). Among cases with RSV subgroup available in South Africa in 2026, the RSV-A subgroup has accounted for a majority of cases, followed by a smaller proportion of RSV-B subgroup viruses (Figure 3).
