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Watch,” was established in Johannesburg (Besselaar et al., 2001; McAnerney et al., 1994; Schoub et al., 1986, 1994). Currently, the Viral Watch network consists of 243 sentinel sites, which provide clinical and epidemiological data on influenza in the community, as well as material for isolation and antigenic and molecular characterization of viruses, for input to WHO for decision making as to annual vaccine composition recommendations. In response to the 2009-H1N1 influenza A pandemic, the Viral Watch program was supplemented with an additional 10 hospital-based sites situated in all 9 provinces. Additional surveillance was provided by a Severe Acute Respiratory Infection (SARI) surveillance program, also established in 2009 in four large hospitals in three provinces. In addition, a large number of diagnostic specimens were received by the laboratory following widespread concern around the pandemic. Finally, active surveillance was introduced to collect information on all laboratory-confirmed cases due to 2009-H1N1 influenza A nationally, from both private and public laboratories.

Up until 2009, the pattern of influenza isolations, as identified through the Viral Watch program, universally showed a typical unimodal distribution, as shown in Figure A10-1, with a median onset at week 23 (range 15-28), a median peak at week 27 (range 20-32) and a median duration of 10 weeks (range 7-17) (Figure A10-2). This pattern is consistent with other temperate Southern Hemisphere countries. The distribution of influenza subtypes is shown in Figure A10-3. Over the past 25 years, H3N2 was the dominant subtype in 13 of the years, H1N1 in 7, and influenza B in 2 of the years, with an equal distribution of all three in 2 years and an equal combination of H3N2 and B in one of the years.

The 2009-H1N1 Influenza A Pandemic in South Africa

The epidemic curve of the 2009-H1N1 influenza A pandemic as determined through active surveillance for all laboratory-confirmed cases nationally in South Africa, as of September 29th, is shown in Figure A10-4. The first case of 2009-H1N1 influenza A was confirmed in South Africa on June 13, some 2 months after that of the United States and a month or more after other Southern Hemisphere countries (Table A10-1). The reason for this inordinate delay in importation into South Africa is probably related to the relatively low volume of air traffic between it and North America (Chen and Wilson, 2008; Khan et al., 2009).

The first confirmed South African case was in a healthy 16-year-old boy who had visited family in Texas and returned to South Africa on June 10th presenting with clinical signs and symptoms of influenza-like-illness (ILI). A positive diagnosis of 2009-H1N1 influenza A infection was made at the National Institute for Communicable Diseases (NICD) using the CDC real-time (RT-) PCR protocol for the detection and characterization of swine influenza. He was treated with oseltamivir on day 3 after onset of symptoms and made an uneventful recovery; no secondary contacts were identified. During the following 2 weeks, NICD continued to detect sporadic (H1N1) among individuals returning from North America,



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