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

Northwestern University

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

Focus of Epidemiological Studies of COVID-19 in Qatar

Raddad L, Chemaitelly H, et al. Characterizing the Qatar Advanced-phase SARS-Sars-CoV-2 Epidemic. 19 July 2020. BioRxiv.  https://doi.org/10.1101/2020.07.16.20155317

Characterizing the Qatar Advanced-phase SARS-Sars-CoV-2 Epidemic

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

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 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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