Asymptomatic transmission of COVID-19 ‘very rare’

The chances of people who have contracted COVID-19 but show no symptoms of the virus infecting others is “very rare”, according to a World Health Organisation scientist

Although a number of people who are tested for the coronavirus test positive with no symptoms, also known as asymptomatic it is believed that these infections are mostly not spread further, but people can transmit the disease to other just before symptoms begin to develop.

Dr Maria Van Kerkhove has said that the evidence comes from countries that carry out “detailed contact tracing”.

Dr Van Kerkhove, who is the WHO’s head of emerging diseases, has made the distinct separations between three categories:

• People who never develop symptoms (asymptomatic)
• People with very mild or atypical symptoms who do not realise they have coronavirus
• People who test positive when they don’t yet have symptoms – but go on to develop them (pre-symptomatic)

This comes after a study conducted in Germany showed that the country’s death-rate could mean that as many as 7.9million Brits have already had the coronavirus without knowing.

Some reports differentiate between the three categories, while others do not, and she said that along with the relatively small sample sizes of people who have been studied, it makes it difficult to draw firm conclusions in regard to the disease.

But Dr Van Kerkhove has said that the weight of the evidence suggests that people who will never develop symptoms of the coronavirus do not play a significant role in the transmitting on COVID-19.

And WHO guidance on wearing masks published at the weekend, says.

“The available evidence from contact tracing reported by member states suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms,”

Through regularly testing a sample of the population, the Office for National Statistics (ONS) has been, it has found that in England, of those who have so far tested positive for the coronavirus, only 29% have been reported to have “any evidence of symptoms” at the time they were tested, or from any previous or additional visits.

According to Professor Babak Javid, an infectious diseases consultant at the University of Cambridge contact-tracing studies from multiple countries suggest that although its “true” that asymptomatic cases “rarely transmit”, infection transmission can happen before or as symptoms of the coronavirus begin to appear or when symptoms are still very minor.

This comes after the New Zealand Ministry of Health has confirmed that they now have no active cases and no new cases of COVID-19 in the country.

Dr Maria Van Kerkhove pointed out since coronavirus “passes through infectious droplets”, and went on to say that it is when those who are infected are coughing or sneezing that they are most able to transmit the disease.

Research shows that it is possible to have detectable amounts of COVID-19 in their system around three days before developing any symptoms of the coronavirus and appear to be capable of transmitting the disease during this period, and the chance of spreading the coronavirus can increase on the day before or on the day that symptoms begin to show.