Delta starts work early, before symptoms begin to show

By Kalani Kumarasinghe
@KalaniWrites on Twitter

Infected persons with the Covid-19 Delta variant begin showing symptoms around five days after infection, the head of the Department of Immunology and Molecular Biology at Sri Jayewardenepura University Dr. Chandima Jeewandara said citing latest research on the pandemic. 

Taking to Twitter, Dr. Jeewandara said that according to latest research, this was reported 1.8 days after a person first tested positive for the viral RNA. “Latest on #delta : on average, people began having symptoms 5.8 days after infection with Delta — 1.8 days after they first tested positive for viral RNA” Dr. Jeewandara tweeted. 

In a series of tweets that followed the Immunology and Molecular Biology expert said that this left approximately two days for an individual to shed viral RNA before the person shows any sign of Covid-19 infection. 

The research emerging globally as well as from the Jayawardenapura University have been a crucial factor in formulating scientific approaches to tackle the disease. 

Understanding the duration of viral shedding of SARS-CoV-2 is therefore vital in the effort to implement effective public health measures to control the spread of the virus. 

What is viral shedding?

When a person is infected with a respiratory disease like the SARS-CoV-2 virus, virus particles will bind to various types of viral receptors — in the case of Covid-19 they bind to receptors lining the respiratory tract. 

The cells in the body hosting the virus will then release infectious virus particles into the environment through talking, sneezing, coughing or even exhaling. However the infected person will not show any symptoms during this time. This process is called viral shedding. 

According to the findings elaborated by Dr. Jeewandara this means that infected persons with the Covid-19 Delta variant have been left with almost two days to release the virus into their surrounding environment before they show any symptoms of being ill. 

Why is this finding important?

Dr. Jeewandara went on to explain that before the emergence of the Delta variant, a person infected with the SARS-CoV-2 virus took an average of 6.3 days to develop symptoms and 5.5 days to test positive for the viral RNA. It left an infected person a narrower window of 0.8 days for viral shedding, unaware that they are affected. 

“As a result, 74% of infections with Delta took place during the presymptomatic phase – a higher proportion than for previous variants,” Dr. Jeewandara said. 

What this means is that the raging speed at which the Delta variant is spread, is helped by this factor, because they are more likely to spread the virus before developing symptoms. Dr. Jeewandara reiterated findings of a study of an outbreak in Guangdong, China, where people were found to be spreading the Delta virus faster, than people infected with earlier versions of the virus. 

According to these findings the researchers have calculated the Delta variant’s basic reproduction number or the R₀ to be 6.4. In simpler terms this is the average number of people to whom every infected person will transfer the virus. The original version of the SARS-CoV-2 virus had a much less R₀ figure which was around 2-4.

Vaccines work!

However in a positive note, Dr. Jeewandara tweeted  “Vaccinated individuals were also 65% less likely than unvaccinated individuals to infect someone else.”

“This is s significant and reassuring finding as Covid-19 vaccines remain effective and a vital part of our response to the pandemic,” he added.