‘70% of Covid-19 patients don’t transmit virus,’ reveals study conducted in AP, TN
A latest study conducted by US-based Centre for Disease, Dynamics and Economic Policy (CDDEP) in Andhra Pradesh and Tamil Nadu has revealed that not all individuals infected with Covid-19 transmit the virus, stating children as active transmitters.
The study, titled ‘Epidemiology and transmission dynamics of Covid-19 in two Indian states’, was published in the September 30 edition of ‘Science’ magazine.
Quoting the findings, an official in the Andhra Pradesh government said a team of investigators from the CDDEP, Andhra Pradesh and Tamil Nadu governments and University of California at Berkeley studied disease transmission patterns in 575,071 individuals exposed to 84,965 confirmed cases of Covid-19 in these two states.
“The study, based on data collected by tens of thousands of contact tracers in the states of Andhra Pradesh and Tamil Nadu, is the largest and most comprehensive analysis of Covid-19 epidemiology till date,” the official claimed.
According to the study, prospective follow-up testing of exposed contacts had revealed that 70 percent of infected individuals did not infect any of their contacts, while 8 percent of infected individuals accounted for 60 percent of observed new infections.
The study found a high prevalence of infection among children who were contacts of cases around their own age. “Risk of transmission from an index case to a close contact ranges from 2.6 percent in the community to 9.0 percent in the household. Same-age contacts are associated with the greatest infection risk,” it said.
However, mortality is higher in the age group of 40-69 years in these two states. It is 0.05 percent among the people in the age group of 5-17 years and 16.6 percent in people of above 85 years. “Men were 62 percent more likely to die than women. Similarly, 63 percent of those who died had at least one co-morbidity, while 36 percent had two or more co-morbidities. Nearly 45 percent of the deceased were diabetic,” the study revealed.
The study found that both Andhra Pradesh and Tamil Nadu have effective primary healthcare delivery models. These two states have the largest healthcare workforces and public health expenditures per capita. They initiated rigorous disease surveillance and contact tracing early in response to the pandemic, it said.
“They have followed procedures including syndromic surveillance and testing for all individuals seeking care for severe acute respiratory illness or influenza-like illness at healthcare facilities, delineation of 5-km “containment zones” surrounding cases for daily house-to-house surveillance to identify individuals with symptoms,” it observed.
The study also noted that there is a daily follow-up of all contacts of laboratory-confirmed or suspected Covid-19 cases, with the aim of testing these individuals 5-14 days after their contact with a primary case, irrespective of symptoms, to identify onward transmission.
According to the director of the CDDEP, Dr Ramanan Laxminarayan, this study was made possible by the significant contact-tracing effort in Andhra Pradesh and Tamil Nadu which involved tens of thousands of healthcare workers.
“The results on disease transmission and mortality have the potential to inform policy to fight Covid-19. The study also speaks to the capacity of research emerging from India to help inform the global response to Covid-19,” he said.