DURBAN - The World Health Organization (WHO) has retracted its statement that the spread of Covid-19 from people who do not show symptoms is "very rare,” this comes after experts have questioned the claim due to a lack of data.
On Monday, Maria van Kerkhove, an infectious disease epidemiologist and the Covid-19 technical lead for the WHO said that the available data from published research and member countries had shown asymptomatic cases were not a significant driver for the spread of the virus.
On Tuesday, Van Kerkhove backtracked on her earlier claims and said she was referring to "very few studies" that tried to follow asymptomatic carriers of the virus over time to see how many additional people were infected.
“I was responding to a question at the press conference, I wasn't stating a policy of WHO. I didn't intend to imply that asymptomatic transmission of the virus globally was 'very rare', but rather that the available data based on modelling studies and member countries had not been able to provide a clear enough picture on the amount of asymptomatic transmission,” she said.
Van Kerkhove was citing modelling data that estimated that anywhere between six percent and 41 percent of the population may be infected but not have symptoms.
With so much still unknown about asymptomatic infection and transmission, many scientists said it was irresponsible for the WHO to speak so definitively because it can erode willingness to take precautions.
Dr Isaac Bogoch, an infectious disease physician at Toronto General Hospital, said there has been confusion over the evolving science on the amount of asymptomatic transmission since the start of the pandemic.
"At a fundamental level, it's extremely important to explain the science well and explain what our current knowledge is and also explain what the unknown questions are.
"I don't think the WHO did a very good job of that yesterday and they did a questionable job of that today when they were trying to clarify their comments," he said.
Some experts say it is not uncommon for infected people to show no symptoms.
A non-peer-reviewed study from Germany in May based on 919 people in the district of Heinsberg — which had among the highest death tolls from Covid-19 in Germany — found that about one in five of those infected were symptomless.
"There's a big question mark at the actual data in real-world observations with asymptomatic [carriers]," said Dr Lynora Saxinger, an infectious disease physician at the University of Alberta.
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