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  • The latest data from the National Institute for Communicable Diseases shows little sign of the traditional winter flu season.
  • The virus may not be spreading as fast thanks to lockdown measures, as well as masks and physical distancing.
  • This is good news for SA's fight against Covid-19.
  • For more articles, go to www.BusinessInsider.co.za.

As masks and physical distancing become part of everyday living in South Africa, it looks like the traditional winter flu season is struggling to take hold. The lockdown has also kept the virus from spreading.

Flu cases usually start to rise sharply around mid-to-late April, but as of end-May there was still little sign of it according to the National Institute for Communicable Diseases, which collects data from sentinel sites that track respiratory diseases around the country.

The NICD says while cases of two flu strains were detected in the Western Cape, the number of cases has been falling since the first week of April.

"There has been no influenza circulating from all other provinces in 2020."

There's an even more marked delay in the onset of seasonal respiratory syncytial virus (RSV), another common pathogen that causes flu-like symptoms, and which can be fatal in young children. South Africa’s RSV season usually starts at the end of February, but by end-May it, too, was nowhere in sight.

"In the previous 3 years the average start of RSV season ranged between week 7 to week 9, therefore the start of the season in 2020 is substantially delayed compared to previous years, possibly in part due to the national lockdown," the NICD says.

Flu normally kills over 10,000 South Africans and costs the economy billions of rands every year due to the deaths and absenteeism from sick days. If fewer people catch flu, the country will have a better chance of fighting Covid-19, experts wrote in April.

Previously, the NICD’s Sibongile Walaza told Business Insider SA: "These are respiratory infections which are transmitted by respiratory droplets and contact. So with limited social interaction as a result of lockdown this should slow down transmission and therefore the number of cases reported."

The drop in international travel could also have contributed, said Richard Lessells, an infectious disease specialist and group leader at the KwaZulu-Natal Research Innovation and Sequencing Platform (KRISP). Seasonal flu has to be introduced into the country by travellers, much like Covid-19 was, he said. "If there’s nobody coming into the country, you won’t have those feeder events."

Walaza cautions that people avoiding going to the doctor during lockdown could have contributed to less flu and RSV being detected. This would mirror what has happened for tuberculosis, where testing numbers more than halved during level 5 lockdown, perhaps because they struggled to get to clinics or because they feared catching Covid-19.

But while that type of behaviour change could have contributed, it’s unlikely to be the main explanation for the non-arrival of the flu season, Lessells said. "We are seeing people turning up [to test for Covid-19], so if they have a flu-like illness there is enough awareness that people are going for testing," he said.

There's also evidence from other parts of the world to suggest that physical distancing and lockdowns can stop the flu. The northern hemisphere’s flu season ended about six weeks earlier than normal this year, Nature reported last week. In Hong Kong, which registered its first Covid-19 case on 23 January, this year's flu season was 63% shorter than usual.

However, even if we’ve been spared the flu so far we’re not out of the woods yet. Opening businesses and schools could fuel its spread, although hygiene measures to curb Covid-19, like washing hands and wearing masks, could help stem it.

This is another factor that policymakers will need to take into consideration when planning how to unlock the economy, Lessells said. "We are facing this delicate balance to make sure the big wave of Covid-19 doesn't intersect with a bad seasonal influenza wave that will overwhelm the system."

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