Prevalence of SARS-CoV-2: An age-stratified, population-based, seroepidemiological survey in Islamabad, Pakistan

Baig, M. A.; Ansari, J. A.; Ikram, A.; Khan, M. A.; Salman, M.; Hussain, Z.; Baig, M. Z. I.; Chaudhry, A.; Malik, M. W.; Akram, K. S.; Saeed, A.; Ranjha, M. A.; Sultan, F.; Sabir, S.

Introduction: Serological surveys are valuable tools to evaluate the extent of disease transmission, measuring preventive effectiveness and proportion of asymptomatic individuals. This age-stratified, serological survey was aimed to measure the COVID-19 distribution and determinants in district Islamabad of Pakistan. Methodology: Three-stage cluster sampling, using population proportionate to size technique, starting with a random number was used. A structured, pretested questionnaire was used after taking informed written consent, to gather demographic, risk factor information. Results: Seroprevalence was found 16.5% (AR: 16.5%/100,000). The mean age was 35 (sd:16 Years). The majority were male (64%), self-employed (29%), and had primary level education (33%). The highest seroprevalence was found in the 21-30 years age group (24.8%) while the 41-50 years age group showed the highest attack rate (112.9/100,000 population). The proportion of the population tested that were asymptomatic was 69% (n=711) while the most frequently reported sign/symptom was cough (99%) followed by fever (20%). No known co-morbidity was reported in 86% (n=884) of respondents while hypertension remained the most reported condition (8%). High seroprevalence was observed in urban areas (12.3%) compared to rural union councils (6.4%). Visiting a house where COVID-19 case was isolated (OR 2, CI 1.38-2.84, P< 0.001), history of contact with a known case of COVID-19 (OR 1.42, CI 1.11-1.82, P=0.005), and attending a mass gathering (OR 1.21, CI: 1.02-1.42, p=0.02) were significant risk factors associated with contracting an infection. A Chi-Square test of independence showed significant protection while using regular hand hygiene practices (6.5; p<0.05) and regular usage of face masks (8.6; p<0.05). Conclusion: Seroprevalence gives a direct estimation of population groups exposed to the virus. A remarkable difference in prevalence is found in urban and rural areas, extreme age groups, and socioeconomic statuses, suggesting targeted public health interventions. Sero-studies are affordable counterparts of molecular testing where quick estimation, prevention effectiveness, and data-driven public health policies are priorities.