ISLAMABAD             -         National Institute of Health (NIH) on Thursday conducted a survey in federal capital to determine the extent of novel coronavirus (COVID-19) infection in the general population, age-specific attack rates and the fraction of asymptomatic or subclinical infections.

A statement issued by NIH said that enhanced surveillance strategy focusing on population-based methods is mandatory to understand the actual situation and then successfully control the pandemic.

Asymptomatic/mild cases of COVID-19 are usually not picked up during routine surveillance and hinder estimation of true population infection rate. Therefore, estimation of true population infection rate is mandatory to effectively guide public health interventions.

To address the above needs, following WHO guidelines, a population-based, age-stratified, sero-epidemiological survey was conducted in Islamabad to determine the extent of infection in the general population, age-specific attack rates and the fraction of asymptomatic or subclinical infections.

The cross-sectional survey was conducted between June 1 and June 25, 2020. The geographic scope of the survey was limited to the Islamabad Capital Territory (ICT). Equal representation from the rural and urban areas was ensured.

According to Pakistan Bureau of Statistics, ICT is divided into 44 administrative units: 12 urban and 32 rural, and as per the National Census 2017-18, the population is 2,006,572 (urban 1,014,825; 50.6% and rural 991,747; 49.4%).

Applying the stratified systematic random sampling using probability proportionate to size technique, a sample of 4,328 was calculated.  A structured, pretested questionnaire was used to gather demographic, clinical, exposure and risk factor data from the community.

Blood samples were collected from each participant and tested for immunoglobulins against SARS-CoV-2 on Chemi-luminescence. Throat/ nasopharyngeal swabs were also collected from those having symptoms or contact history with a positive case for PCR testing. All samples were tested at virology lab, PHLD at National Institute of Health.

Preliminary analysis showed a prevalence of COVID-19 to be 14.5 per 100 persons. As for the area wise distribution of the disease, rural union councils were more affected. Out of all the union councils, Chattar was found to be most affected followed by union councils Muhrian and Tarlai Khurd. Considering age, the most affected group was 41-50 years followed by 31-40 years and 51-60 years age groups. RT-PCR positivity rate was found to be 17 per cent.

The results of the survey showed that the calculated prevalence of COVID-19 in ICT is 14.5 per cent which translates to 290,000 individuals in ICT have been exposed to the SARS-CoV-2 virus and have developed the immunoglobulins against the virus.

This should be seen in the context that a vast majority of the individual already exposed to the virus are asymptomatic and therefore escape detection. This was one of the objectives of this survey to uncover the hidden/already exposed individuals in the communities and these must not be taken as new cases/patients.