About 20 per cent of the 5.4 crore population in Andhra Pradesh is projected to have been infected by the Covid-19 virus.
The estimate is based on a sero survey conducted in two phases in August, with a total of about 59,000 samples collected from the 13 districts in the state.
The per centage of asymptomatic persons among those who tested positive varied between 90 to 100 per cent in these districts. All those who tested positive from among the 5000 people in Chittoor district have shown no signs of the illness.
Vizianagaram tops; Nellore at the bottom
Overall Covid-19 prevalence in AP is pegged at 19.7 per cent.
Vizianagaram emerged at the top with 30.6 per cent people there assessed to have developed antibodies against the Covid-19 virus.
Incidentally, Vizianagaram, a relatively small district in north coastal Andhra Pradesh, was the last to report a positive case - on 6 May.
Kurnool, which is one of the worst affected districts, came second with 28.1 per cent prevalence.
Nellore district which reported the first Covid-19 case in Andhra Pradesh in the middle of March, has shown only 8.2 per cent sero prevalence.
Sero surveillance provides estimates of antibody levels against infectious diseases and is considered the gold standard for measuring population immunity due to past infection or vaccination, officials said.
The present process involves testing blood (serum/plasma) samples from thousands of people for the SARS-CoV-2 antibodies. These surveys provide information on the proportion of population that may have acquired Covid-19 immunity and help track the same over time.
“The sero survey results are helpful in understanding the infection spread and thereby in the planning of required medical infrastructure, Covid-19 care in the districts,” said Bhaskar Katamneni, commissioner, health and family welfare, Andhra Pradesh.
Prevalence bit higher among females
A slightly higher number of women (19.9 per cent) are stated to have been infected than males (19.5). The occurrence among the high-risk population i.e., senior citizens, and those with comorbid conditions is 20.3 per cent.
The Covid-19 prevalence is found to be 22.5 per cent in the urban areas and 18.2 in rural.
While around 3500 samples were examined from each of Anantapuram, East Godavari, Krishna and Nellore districts between 5 to 15 August; 5,000 samples each were tested from Chittoor, West Godavari, Srikakulam, Visakhapatnam, Vizianagaram, Guntur, Prakasam, Kurnool and Kadapa from 26 to 31 August.
As of Friday, Andhra Pradesh has recorded a total 5.47 lakh positive cases. While active cases are 96,191, the state has 4,779 Covid-19 related deaths.