An estimated 1.93 crore people or 27% of the population in Karnataka are currently infected with Covid-19 or had contracted the disease in the past, a government-backed study has said.
The study was based on a state-wide serosurvey conducted from September 3 to September 16 to estimate the prevalence of Covid-19.
“Of the 7.07 crore estimated population in Karnataka, the study estimates that 1.93 crore are either currently infected or already had the infection, as of September 16,” said Dr Giridhar Babu, principal investigator of the study and member of the state Covid-19 technical advisory committee.
While 16.4% of the 15,624 survey samples showed that the subjects were infected in the past and had developed IgG antibodies against SARS-CoV-2 virus, 12.7% of the apparently healthy population in the surveyed area had an acute and active infection.
Health and Medical Education Minister Dr K Sudhakar, while releasing the findings on Wednesday, said, “The sampled population surveyed were all adults aged 18 years and above. All 30 districts of the state, including eight zones of the BBMP, were surveyed. The survey was conducted in 290 hospitals and selected population settings.”
Three groups of population were covered — low-risk group, i.e., pregnant women attending antenatal clinics, people attending outpatient departments in hospitals/attendees of children or patients; moderate-risk group, i.e., people moving in the community like bus conductors, vendors in vegetable markets, healthcare workers, individuals in containment zones and congregate settings such as markets, malls, retail stores, bus stops, railway stations, pourakarmikas/waste collectors; and high-risk group, i.e., the elderly and those with co-morbid conditions.
The study used Rapid Antigen Test and RT-PCR for diagnosis of acute infection. Serum testing for IgG antibodies was conducted to know the protection offered by the immune response.
Of the 16,585 people surveyed covering three risk categories, analysis was done on results for 15,624 whose RAT and RT-PCR, and antibody test results were available.
The overall adjusted prevalence of Covid-19 was 27.3% (combined IgG and active infection). At the state level, it was estimated that there were 40 undetected infected individuals for every RT-PCR confirmed case, i.e., the case-to-undetected-infections ratio (CIR) was 1:40. The cases-to-infections ratio ranged from 10 to 111 across districts.
Districts with high cases to infections ratio (i.e., more than 40) need to improve detection of cases actively through syndromic approach and improve testing. These districts were Vijayapura, Belagavi, Chitradurga, Tumakuru, Raichur, Ramanagar, Haveri, Chamarajanagar, Bidar, Davangere, Yadgir, Kalaburagi, Kolar, Kodagu, Mandya, Chikkamagalur, Ballari, Bengaluru Rural and Hassan.
Sudhakar said that a follow-up survey is planned to measure the extent and speed of transmission and evaluate the impact of containment strategies over time in the state. This will be done in December-end and February-March.
The survey was a collaborative effort of the Department of Health and Family Welfare, Indian Institute of Public Health, Nimhans, Indian Institute of Science, Indian Statistical Institute, Unicef, MS Ramaiah Medical College and others.