By July 10 397,577 people had been tested for COVID-19 (14.2% of population of Qatar). 110,986 tested PCR-positive (4.0% of population), which yields a positivity rate of 27.9%. This rate increased and peaked on May 22, after which it has been declining and was 17.8%. on July 9. 
Males were 1.6 fold more likely to test PCR-positive, and Nepalese and Bangladeshis were most likely to test PCR positive.

Analysis of the national SARS-CoV-2 PCR testing and hospitalization database

1,307 people participated in the community surveys varying in sex, age, nationality, and education. Some were randomly invited and some participated via an open announcement, but no major differences existed between these two groups.
156 people tested positive for SARS-CoV-2, resulting in a 14.9% prevalence. " After controlling for confounders, strong evidence for an association with positivity (p-value ≤0.05) was found for nationality, educational attainment, occupation, presence of symptoms, and seeking medical attention, but
not for sex, age, study recruitment/invitation, PHCC center location, seeking hospitalization, or history of contact with an index case. The differences were pronounced for nationality, occupation, presence of symptoms, and seeking medical attention."
"The proportion of asymptomatic individuals was 58.5% in those testing positive and 79.5% in those testing negative". Reporting 3+ symptoms was associated significantly with infection. 

PCR positivity in community survey

390 random PCR testing campaign were conducted in workplaces testing 22,834 individuals, and 48 campaigns in residential areas testing 3, 881 individuals. At least 1 infected individual was found in 72.3% of workplaces and 72.4% of residential areas. There was no evidence for differences in PCR point prevalence between the workplaces and residential areas, consistent with a widely disseminated epidemic. 

PCR positivity in the ad-hoc testing campaigns in workplaces and in residential areas

"A total of 32,970 individuals were tested for SARS-CoV-2 antibodies with the blood specimens drawn between May 12-July 12, with a median day of June 28. A total of 5,448 individuals had detectable antibodies. The weighted (for total population of Qatar) antibody prevalence was 24.0%". There were significant differences in antibody prevalence by sex and nationality. After controlling for confounders, odds of antibody positivity in males were 2.9-fold higher than females, and were highest among Bangladeshis and Nepalese, lowest among Qataris. Odds also increased incrementally with age.  Overall, antibody positivity was >88% among those who had their first positive PCR test >15 days before the antibody test." 

Anti-SARS-CoV-2 seropositivity

- National SARS-CoV-2 PCR testing and hospitalization database
- Community surveys
- Ad-hoc testing campaigns in workplaces and in residential areas
- Seroprevalence survey

Northwestern University

- crude severity rate
- crude fatality rate
- sex
- age
- nationality 
- by testing method
- discussion

Focus of Epidemiological Studies of COVID-19 in Qatar

Via Testing Method

- An analysis of the national SARS-CoV-2 PCR testing and hospitalization database showed that males were 1.6-fold more likely to test PCR positive than females. 
- Odds of anti-SARS-CoV-2 seropositivity in males were 2.9-fold higher than females
- Males had 1.6-fold higher odds for developing severe and critical infection compared to females but no difference was observed for death, possibly because of the small number of deaths 

- An analysis of the national SARS-CoV-2 PCR testing and hospitalization database revealed that the odds of PCR positivity varied by nationality and were highest among Nepalese and Bangladeshis, and lowest among Qataris compared to other nationalities
- Odds of anti-SARS-CoV-2 seropositivity highest among Bangladeshis and Nepalese, lowest among Qataris
-Overall, there were no major differences in severe, critical, or fatal infection odds by nationality,
but there was evidence for higher risk of serious disease for Bangladeshis and Filipinos, and lower risk for Indians

Nationality 

After controlling for confounders, age was, by far, the strongest predictor of severe, critical, or fatal infection and more so for critical infection and death. The risk most greatly increased for those over 50 years of age, which represents 8.8% of Qatar's population.

- crude severity rate: cumulative number of
severe and critical infections over the cumulative number of laboratory-confirmed infections
- 3.4% on July 5

Crude Severity Rate 

-  cumulative number of COVID-19 deaths over the cumulative number of laboratory-confirmed infections
- varied over course of pandemic 
- 0.14% as of July 10

Crude Fatality Rate

 Temporal trend in A) crude case severity rate, B) crude case fatality rate, C) infection severity rate, and D) infection fatality rate in Qatar.

Trends in severity and fatality rates

All these individual methods of investigation came to similar findings:
- Qatar has experienced a pervasive SARS-CoV-2 epidemic that is rapidly declining, probably due to exhaustion of susceptibles
- It was composed of two separate but overlapping sub-epidemics: a rapid growing epidemic among the labor population, and a slower growing epidemic among the urban population

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