Coronavirus far more common than what is shown in PCR test statistics – The Island
A seroprevalence rate of 24.5% was observed in the CMC in late January 2021 in all age groups, according to a study by Sri Lankan and UK researchers. This is a much higher number than the PCR tests indicated.
The research was conducted in the city of Colombo, which has seen the most coronavirus cases by the end of January 2021, the researchers said. Although Sri Lanka had successfully contained the pandemic by the end of September with no local cases detected from August to September 2020, an explosive spread began in early October and quickly spread across the country.
“However, since Colombo is the country’s commercial capital and also due to the extremely overcrowded living conditions, 32,346 / 89,817 (36.01%) locally discovered cases came from Colombo at the end of March 2021. Of the cases in the Colombo district, 14,416 (44.6%) were identified within the city. We did a sero survey prior to the start of the vaccination program to understand the extent of the SARS-CoV-2 outbreak, “they said.
The researchers added that although the seropositivity rate was highest in the 10-20 age group (34.03%), the PCR positivity rate was 9.80%. Hence, the PCR positivity rates seem to underestimate the true extent of the outbreak and the age groups infected. They said that in many countries, the number of cases reported does not necessarily reflect the extent of the outbreak, the age groups infected and the risk groups, as most infections are asymptomatic and real-time quantitative PCR for SARS is limited. CoV2. It has been estimated that monitoring SARS-CoV2 with qRT-PCR alone can underestimate its true prevalence by ten fold.
“Differences in the PCR positivity rates and seropositivity rates were also observed in 60-70 year-olds (8.90 vs. 30.4%) and in people aged 70 years (4.10 vs. 1.20%). The female seropositivity rate was 29.70% (290/976), which was significantly higher than the male’s 21.2% (333 / 1,571), the researchers said.
It is important to conduct serosurveillance studies to understand the true extent of an outbreak, to understand the future outbreaks that may occur in a given area, and to further understand the dynamics of transmission and duration of immunity, the researchers said.
“Based on seropositivity rates of 24.46%, 138,276 people are likely infected, compared to the reported PCR-positive cases of 14,416. Hence, the infection detection rates by PCR seem to have underestimated the actual number of infections by 9.59 times, which is not surprising since the random PCRs were performed mainly in the working population and less often in the domestic population. ”They claimed that Samples for PCR were only taken on certain days of the week when the team visited the condominiums and residential areas, the population subjected to PCR most days was mainly the working population. Blood samples were obtained from these participants at the same time as the sample was collected for these routine random PCR tests for SARS-CoV-2. None of the participants had symptoms at the time the blood was drawn and had not previously been infected with the SARS-CoV-2 virus.
The researchers further claimed that the city of Colombo is divided into six districts: namely D1, D2A, D2B, D3, D4 and D5. Although the overall seroprevalence was 24.46%, certain districts in the CMC (D2A, D2B, and D3) had higher seroprevalence rates (26.2–39%) compared to D4, which had a seroprevalence rate of only 3.33%. These overall differences between counties reflected the population density and housing conditions in those counties, with counties with high seroprevalence having more overcrowded areas with poor housing conditions. The differences in the seroprevalence rates in different districts could also be due to differences in the control measurements used. For example, in D1, certain areas in that district had a very high infection rate, even though the seroprevalence was 14.76% as determined by PCR positivity. Due to the early detection of SARS-CoV-2 infection in certain areas in this district, these areas were isolated very early, which would have contained the spread to the rest of the D1 district, resulting in fewer infections. Such similar differences have been observed in many states of India, where the slum areas had seroprevalence rates between 52.6 and 58.7%, compared with 12-17.9% in non-slum areas, it was higher than in many areas in Europe (Spain, Sweden, Switzerland and Germany), which reported a seroprevalence between 5 and 13.6%, and Iran (22.16%), which reported higher infection rates (14-17). However, the use of different antibody assays, which showed different degrees of sensitivity and specificity in these different studies, could lead to such differences.
Chandima Jeewandara, Dinuka Guruge, Inoka Sepali Abyrathna, Saubhagya Danasekara, Banuri Gunasekera, Pradeep Darshana Pushpakumara, Deshan Madhusanka, Deshni Jayathilaka, Thushali Ranasinghe, Gayasha Somathilake, Shyrar Ribanya, Michael Tanya Tanya, Ti were Schimanski, TK Tan, Pramila Rijal, Julie Xiao, Graham S. Ogg, Alain Townsend and Gathsaurie Neelika Malavige. (RK)