In Karnataka, around 1.93 crore people, 27 per cent of the state's population, are currently infected with COVID-19 or have had the infection in the past.
The first sero-survey to estimate the prevalence of COVID-19 in the state was conducted between September 3 and 16. While the Rapid Antigen Test and RT-PCR tests were carried out for diagnosing acute infections, serum testing for IgG antibodies was conducted to study the protection offered by the immune response.
Health and medical education minister Dr K Sudhakar, said Karnataka has "captured the total prevalence, which includes information on both current and past infections. In the surveyed population, 16.4 per cent of the people were found to be infected in the past and had IgG antibodies against SARS CoV-2."
"Around 12.7 per cent of the healthy population in the surveyed area was found to have a current (active) infection. The overall adjusted prevalence of COVID-19 (combined IgG and active infection) is 27.3 per cent. The infection fatality rate due to COVID-19 in the state of Karnataka is 0.05," he added.
The survey was a collaborative effort of the Department of Health and Family Welfare, Indian Institute of Public Health-Bangalore, Indian Institute of Science, Indian Statistical Institute (BC), UNICEF, MS Ramaiah Medical College, Bangalore Medical College, and others.
The sample population of 16,585 adults aged 18 years and above from across 30 districts were picked for the survey conducted in 290 hospitals and select population groups covering the three risk categories—low risk group (pregnant women attending the antenatal clinic, OPD patients, patient attendees in hospitals), moderate-risk groups (bus conductors, vegetable market vendors , health care workers, individuals in containment zones, markets, malls, retail stores, bus stops, railway stations, pourakarmikas/waste collectors) and high-risk groups like the elderly and persons with co-morbidities.
According to the findings, there are 40 undetected infected individuals for every RT-PCR confirmed case. The districts of Vijayapura, Belagavi, Chitradurga, Tumakuru, Raichur, Ramanagar, Haveri, Chamarajanagar, Bidar, Davanagere, Yadgir, Kalaburagi, Kolar, Kodagu, Mandya, Chikmagalur, Ballari, Bengaluru Rural, Hassan have high cases to infection ratio (more than 1:40) and they need to improve detection of cases through syndromic approach, improve testing, and ensure public health actions like wearing masks and maintaining social distancing and hand washing. The districts with a low case-to-infection ratio like Bengaluru Urban and Mysuru suggest that their strategy for testing has been reasonable and can be replicated in other districts.
The study indicates that the state is passing through different stages of the COVID-19 pandemic in the different districts and that the surge in cases is yet to occur in the districts with the lowest estimated prevalence of COVID-19 (Dharwad, Gadag, Chikkaballapur, Bagalkot, and BBMP Mahadevapura). The study recommends establishing the district-level facility-based sentinel sero-surveillance to monitor the trend of infection in the long term systematically, which can help in local decision-making and public health response.
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.
