Characterizing the Qatar advanced-phase SARS-CoV-2 epidemic
Authors: Abu Raddad Laith J. , Chemaitelly Hiam , Ayoub Houssein H. , Kanaani Zaina Al , Khal Abdullatif Al , Kuwari Einas Al , Butt Adeel A. , Coyle Peter , Jeremijenko Andrew , Kaleeckal Anvar Hassan , Latif Ali Nizar , Owen Robert C. , Abdul Rahim Hanan F. , Al Abdulla Samya A. , Al Kuwari Mohamed G. , Kandy Mujeeb C. , Saeb Hatoun , Ahmed Shazia Nadeem N. , Al Romaihi Hamad Eid , Bansal Devendra , Dalton Louise , Al Thani Sheikh Mohammad , Bertollini Roberto 
Published: July 2020

Background

Qatar has a population of 2.8 million, over half of whom are expatriate craft and manual workers (CMW). We aimed to characterize the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in Qatar.

Methods

A series of epidemiologic studies were conducted including analysis of the national SARS-CoV-2 PCR testing and hospitalization database, community surveys assessing current infection, ad-hoc PCR testing campaigns in workplaces and residential areas, serological testing for antibody on blood specimens collected for routine clinical screening/management, national Coronavirus Diseases 2019 (COVID-19) death registry, and a mathematical model.

Results

By July 10, 397,577 individuals had been PCR tested for SARS-CoV-2, of whom 110,986 were positive, a positivity cumulative rate of 27.9% (95% CI: 27.8-28.1%). PCR positivity of nasopharyngeal swabs in a national community survey (May 6-7) including 1,307 participants was 14.9% (95% CI: 11.5-19.0%); 58.5% of those testing positive were asymptomatic. Across 448 ad-hoc PCR testing campaigns in workplaces and residential areas including 26,715 individuals, pooled mean PCR positivity was 15.6% (95% CI: 13.7-17.7%). SARS-CoV-2 antibody prevalence was 24.0% (95% CI: 23.3-24.6%) in 32,970 residual clinical blood specimens. Antibody prevalence was only 47.3% (95% CI: 46.2-48.5%) in those who had at least one PCR positive result, but it was 91.3% (95% CI: 89.5-92.9%) among those who were PCR positive >3 weeks before serology testing. There were substantial differences in exposure to infection by nationality and sex, reflecting risk differentials between the craft/manual workers and urban populations. As of July 5, case severity rate, based on the WHO severity classification, was 3.4% and case fatality rate was 1.4 per 1,000 persons. Model-estimated daily number of infections and active-infection prevalence peaked at 22,630 and 5.7%, respectively, on May 21 and May 23. Attack rate (ever infection) was estimated at 53.5% on July 12. R0 ranged between 1.45-1.68 throughout the epidemic. Rt was estimated at 0.70 on June 15, which was hence set as onset date for easing of restrictions. Age was by far the strongest predictor of severe, critical, or fatal infection.

Conclusions

Qatar has experienced a large SARS-CoV-2 epidemic that is rapidly declining, apparently due to exhaustion of susceptibles. The epidemic demonstrated a classic susceptible-infected-recovered “SIR” dynamics with a rather stable R0 of about 1.6. The young demographic structure of the population, in addition to a resourced public health response, yielded a milder disease burden and lower mortality than elsewhere.