Prof Karim explains why SA's Covid-19 community transmissions are low
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Johannesburg - Health experts have noted the national lockdown as one of the reasons for the decline in the spread of Covid-19 infection cases. But the growth of community transmission is unavoidable, Professor Salim Abdool Karim warned on Monday night.
Karim is an expert epidemiologist and one of several advisors to Health Minister Dr Zweli Mkhize.
He said the rate of infections in the country had not taken the expected trajectory. He said South Africa was a unique case in that instead of case numbers rising uncontrollably, such as in the UK or Italy, the country had reached a plateau in cases.
He attributed this to stringent measures taken by the government especially with the national lockdown.
Karim said in looking at the stages that a virus spreads, the first phase would be the travellers who brought the virus into the country. The second stage, he said, would be those who come into contact with the travellers and the third stage would be the community transmissions.
He said the country was currently experiencing the last wave of travel infections and that community contacts were expected to rise but they did not.
“We expected to see an exponential growth in our epidemic. For some reasons, those two groups (the first and third) did not lead to a widespread community epidemic. We still see community transmissions but they are at a low level. If it did we would have been on a rapid upward trajectory. The daily number of cases before the lockdown was 65. The number of cases after the lockdown is 72 cases,” Karim said.
“The reproductive rate of infection is one of the important things to look out for in an epidemic. How many people is the infected person infecting? If each infected person infects one other person that rate of infection remains at a static level. If one infected person is infecting more than one person the infection grows. And if one infected person infects less than one person the epidemic goes into a decline.
“When we look at our numbers we can assume that each infected person is infecting one person that is why we are seeing this line. Why? That was the reason why we instituted all the measures such as social distancing and so on. When you think of a lockdown each infected person becomes a dead end because they are not interacting with others. If community transmission is low cases decline. If community transmissions increase then cases will increase exponentially the curve will start again,” Karim explained.
Karim said there were three areas which concerned the health department which had been flagged as areas where an increase in community transmissions is expected to be seen. These areas were the greater Johannesburg area, greater Cape Town and eThekwini.
He said an end to the lockdown was inevitable and as such the number of infections would rise.