The World Health Organisation recommends outpatient influenza-like illness (ILI) and inpatient
severe acute respiratory illness (SARI) surveillance. We evaluated two influenza surveillance
systems in South Africa: one for ILI and another for SARI.
The Viral Watch (VW) programme has collected virological influenza surveillance data voluntarily
from patients with ILI since 1984 in private and public clinics in all 9 South African
provinces. The SARI surveillance programme has collected epidemiological and virological
influenza surveillance data since 2009 in public hospitals in 4 provinces by dedicated personnel.
We compared nine surveillance system attributes from 2009–2012.
We analysed data from 18,293 SARI patients and 9,104 ILI patients. The annual proportion
of samples testing positive for influenza was higher for VW (mean 41%) than SARI
(mean 8%) and generally exceeded the seasonal threshold from May to September (VW:
weeks 21–40; SARI: weeks 23–39). Data quality was a major strength of SARI (most data
completion measures >90%; adherence to definitions: 88–89%) and a relative weakness of
the VW programme (62% of forms complete, with limited epidemiologic data collected;
adherence to definitions: 65–82%). Timeliness was a relative strength of both systems (e.g.
both collected >93% of all respiratory specimens within 7 days of symptom onset). ILI surveillance was more nationally representative, financially sustainable and expandable
than the SARI system. Though the SARI programme is not nationally representative, the
high quality and detail of SARI data collection sheds light on the local burden and epidemiology
of severe influenza-associated disease.
To best monitor influenza in South Africa, we propose that both ILI and SARI should be
under surveillance. Improving ILI surveillance will require better quality and more systematic
data collection, and SARI surveillance should be expanded to be more nationally representative,
even if this requires scaling back on information gathered.
S1 Table. Minimum data collection standards  for ILI and SARI surveillance.
S2 Table. Influenza cases detected by subtype from SARI and ILI surveillance programmes
(2009–2012), South Africa.
S3 Table. SARI and ILI case definitions used for screening and enrolment by the SARI and
Viral Watch surveillance programmes respectively, South Africa, 2009–2012.