24 Nov Epidemiology, clinical characteristics and risk factors of coronavirus disease 2019 (COVID- 19) in Casablanca
S. Djorwé , A. Bousfiha , N. Nzoyikorera , V. Nkurunziza , K. A Mouss , B. Kawthar and A. Malki
Abstract: This is an analytical cross-sectional study of coronavirus disease 2019 (COVID-19) based on data collected between 1 November 2020 and 31 March 2021 in Casablanca focusing on the disease’s epidemiological status and risk factors. A total of 4569 samples were collected and analysed by reverse-transcription polymerase chain reaction (RT-PCR); 967 patients were positive, representing a prevalence of 21.2 % for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The mean age was 47.5±18 years, and infection was more common in young adults (<60 years). However, all age groups were at risk of COVID-19, and in terms of disease severity, the elderly were at greater risk because of potential underlying health problems. Among the clinical signs reported in this study, loss of taste and/or smell, fever, cough and fatigue were highly significant predictors of a positive COVID-19 test result (P<0.001). An assessment of the reported symptoms revealed that 27 % of COVID-19-positive patients (n=261) experienced loss of taste and/or smell, whereas only 2 % (n=72) of COVID-19-negative patients did (P<0.001). This result was consistent between univariate (OR=18.125) and multivariate (adjusted OR=10.484) logistic regression analyses, indicating that loss of taste and/or smell is associated with a more than 10-fold higher multivariate adjusted probability of a positive COVID-19 test (adjusted OR=10.48; P<0.001). Binary logistic regression model analysis based on clinical signs revealed that loss of taste and/or smell had a performance index of 0.846 with a P<0.001, confirming the diagnostic utility of this symptom for the prediction of COVID-19-positive status. In conclusion, symptom evaluation and a RT-PCR [taking into account cycle threshold (Ct) values of the PCR proxy] test remain the most useful screening tools for diagnosing COVID-19. However, loss of taste/smell, fatigue, fever and cough remain the strongest independent predictors of a positive COVID-19 result.
Study population and samplingThis is a retrospective analytical study that was conducted on subjects wishing to be screened for various reasons: either because they suspected they had a clinical sign of COVID-19 infection, or because they had been in recent contact with COVID-19-positive subjects, or because they wanted to travel, or for other miscellaneous reasons. This study was conducted over a period of 5 months from 1 November 2020 to 31 March 2021. The samples were obtained using nasopharyngeal swabs and were collected in tubes containing stable universal viral transport media (Nal von MindenGmbH, Germany) after recording clinical and demographic information. All samples received were processed in a room equipped with a level 2 biosafety facility, according to the required standards of the molecular biology unit. All samples were accompanied by information forms for the performance of a virological examination of COVID-19 by RT-PCR. The information form included the following information: patient ID, gender, age, reason for testing, presence of signs or symptoms. A patient was classified as asymptomatic if he or she was infected with SARS-CoV-2, but did not have symptoms of COVID-19, while a symptomatic patient had signs and symptoms of COVID-19. All information was entered into LIS (a specialized platform for the management of COVID-19 analyses set up by the Moroccan Ministry of Health and designed by ENOVA Research and Technology in 2020). The final database used was extracted from LIS in Excel format.
Results:
General characteristics of the COVID-19 cases detected
A total of 4569 samples were collected to search for SARS-CoV-2 by RT-PCR between 1 November 2020 and 31 March 2021, of which 2369 (51.8 %) were from women and 2200 (48.2 %) were from men. The samples were collected in the Casablanca-Settat region. Of the 4569 patients examined, 3352 (73.4 %) were asymptomatic cases, which was significantly (P<0.001) higher (73.4 %, n=3352) than symptomatic cases (26.6 %; n=1217). Among the analysed samples, 967 out of 4569 samples were positive, giving a prevalence rate of 21.2 % (95 % CI=20–22.4 %). The mean age±standard deviation of the COVID-19-positive patients was 47.5±18 years (range: 3–91 years), with a median age of 48 years. By contrast, the mean age±standard deviation of the COVID-19-negative patients was 42.3±17.5 years (range: 2–97 years), with a median age of 40 years. Among the 4569 samples analysed, most were obtained from the 31–40 (20.5 %) age group, whereas few were obtained from the ≤10 (0.7 %) and 91–100 (0.2 %) age groups (Table 1). In general, the distribution of age by sex was approximately the same (Mann–Whitney test, P<0.05). However, there was a significant difference in the proportion of COVID-19-positive patients between the sexes (Mann–Whitney test, P<0.001). Furthermore, among the 967 confirmed cases, 66.2 % (n=640) were symptomatic cases and 33.8 % (n=327) were asymptomatic cases, demonstrating a high percentage of symptomatic cases [95 % CI=32.4 % (25.91–38.46 %); P<0.001]. Among 4569 samples analysed, 34 were children, with 79.4 % (n=27) asymptomatic cases and 20.6 % (n=7) symptomatic cases identified. Among the five positive cases in children, all were asymptomatic. In terms of symptom categories, patients with the smallest Ct values (10≤Ct<20) were recorded in symptomatic subjects, showing that these subjects had a statistically higher viral load than asymptomatic subjects (P<0.001).
Conclusion: In this study, there was a higher prevalence of COVID-19 than the national prevalence. However, young adults (<60 years) were more likely to contract COVID-19 than other age groups. Particular attention was paid to functional clinical signs, including loss of taste and/or smell, which, among other functional signs (fever, fatigue, cough), was the strongest predictor of SARS-CoV-2 infection in patients with suspected COVID-19. It would be wise to take these symptoms into account at diagnosis to minimize the delay in the diagnosis. On the other hand, the interpretation of results following SARS-CoV-2 infection associated with the clinical context and Ct values was defined as a relevant algorithm for COVID-19 diagnosis in this study. This association between Ct values (viral load) and clinical context would allow the establishment of an adapted management scheme for patients according to their medical history. In addition, this study provided significant results that will be used to complement previous studies conducted in Morocco to monitor the epidemiological situation while improving the quality of diagnosis (early, accurate and rapid diagnosis, followed by early isolation) and the identification of epidemio-clinical characteristics for a better understanding of clinical outcomes to overcome the pandemic.
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