ECONOMYNEXT – People who contract the delta variant of SARS-CoV-2, the virus that causes COVID-19, begin to develop symptoms 5.8 days after infection and 1.8 days after testing positive for viral RNA, while vaccinated people are 65% less likely to infect others, an expert in Sri Lanka said.
This leaves almost two days for infected people to shed viral RNA before they show any symptoms, Director of the Allergy Immunology and Cell Biology Unit at the University of Sri Jayawardenapura Dr Chandima Jeewandara tweeted on Friday (20).
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
— Chandima Jeewandara (@chandi2012) August 20, 2021
RNA is a ribonucleic acid or a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information. Diseases such as COVID-19 are caused by RNA viruses.
According to Jeewandara, patients who got infected with strains of SARS-CoV-2 that came before delta took an average of 6.3 days to develop symptoms and 5.5 days to test positive for viral RNA. Prevoius strains had a narrower window of just 0.8 days for oblivious viral shedding.
“As a result, 74% of infections with delta took place during the presymptomatic phase — a higher proportion than for previous variants,” he said.
Jeewandara further said the R0 of delta is 6.4 while the orginal virus had an R0 of 2 to 4.
R0, pronounced “R naught,” is a mathematical term that indicates how contagious an infectious disease is. It’s also referred to as the reproduction number. As an infection is transmitted to new people, it reproduces itself.
R0 tells you the average number of people who will contract a contagious disease from one person with that disease. It specifically applies to a population of people who were previously free of infection and haven’t been vaccinated.
For example, if a disease has an R0 of 18, a person who has the disease will transmit it to an average of 18 other people. That replication will continue if no one has been vaccinated against the disease or is already immune to it in their community.
Sri Lanka is going through a devastating third wave of COVID-19, with rapidly spreading cases suspected to be delta.
Health authorities have vaccinated 12,053,137 with the first dose of one of five COVID-19 vaccines while 5,311,784 have received both doses.
Quoting an analysis done medRxiv, Dr Jeewandara said latest findings have revealed that vaccinated individuals were 65% less likely than unvaccinated individuals to infect another person.
The analysis was done with 167 patients infected with the delta variant in the Guangdong, China outbreak.
The mean estimates of the latent period and the incubation period were 4.0 days and 5.8 days, respectively. A relatively higher viral load was observed in Delta cases than in wild-type infections. The secondary attack rate among close contacts of Delta cases was 1.4 percent, and 73.9 percent (95 percent confidence interval: 67.2 percent, 81.3 percent) of the transmissions occurred before onset.
Index cases without vaccination (OR: 2.84, 95 percent confidence interval: 1.19, 8.45) or with one dose of vaccination (OR: 6.02, 95 percent confidence interval: 2.45, 18.16) were more likely to transmit infection to their contacts than those who had received 2 doses of vaccination.
According to the World Health Organisation’s Weekly Epidemiology update,148 countries (three new countries) have reported cases of the delta variant, while cases of the alpha variant have been reported in 190 countries, territories or areas. Up to 138 countries (one new country) have reported cases of the Beta variant, while 82 countries (one new country) have reported cases of the Gamma variant. (Colombo/ Aug 20/2021)