#Coronavirus in South Africa: Scientists explore surprise theory for low death rate - BBC News
▻https://www.bbc.com/news/world-africa-53998374
It is almost certain that many factors - particularly the quick lockdowns as well as youthful demographics - are likely to have contributed to South Africa’s successes in tackling the virus thus far.
But in recent days, scientists at Vaccine and Infectious Disease Analytics unit, at Baragwanath hospital in Soweto, have been wondering if one missing factor might lie inside a glorified chest freezer in their laboratory, on the outskirts of Johannesburg.
The freezer - whose temperature is kept at minus 180 degrees centigrade, thanks to liquid nitrogen - contains metal cannisters storing five-year-old human blood samples. Or to be more specific, extracts from blood cells - known as PBMCs - acquired during an earlier influenza vaccine trial in Soweto.
The idea is that, by studying the PBMCs, the scientists might find evidence that people had been widely infected by other coronaviruses - those, for instance, responsible for many common colds - and that, as a result, they might enjoy some degree of immunity to #Covid-19.
“It’s a hypothesis. Some level of pre-existing cross-protective immunity… might explain why the epidemic didn’t unfold (the way it did in other parts of the world),” said Professor Madhi, explaining that data from scientists in the United States appeared to support the hypothesis of some pre-existing immunity.
Colds and flu are, of course, commonplace around the world. But the South African scientists wondered whether, because those viruses spread more effectively in over-crowded neighbourhoods where it is harder for people to self-isolate, there might be an extra degree of immunity towards Covid-19.
“The protection might be much more intense in highly populated areas, in African settings. It might explain why the majority (on the continent) have asymptomatic or mild infections,” Professor Madhi said.
"I can’t think of anything else that would explain the numbers of completely asymptomatic people we’re seeing. The numbers are completely unbelievable,"he said, expressing cautious hope that some of the challenges that have so often held back poorer communities might now work in their favour.
Sceptics - and there are plenty with any hypothesis like this - might point to countries like Brazil, with its crowded favelas, and its high infection rate.