Understanding the dynamics of coronavirus disease 2019 (COVID-19) emergence requires investigation with regard to the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the accuracy of detection tests. This research aims to evaluate the impact of some demographic factors and seasonal fluctuations on the positivity and efficacy of diagnostic tests. The study included a total of 14,642 participants from extreme west of Algeria, comprising 4,799 individuals positively diagnosed for COVID-19 and 9,843 negative controls. Our results demonstrated that women were more likely to be infected with COVID-19 (OR=8.32; 95% CI: 7.43-9.33; p=0.0001), indicating a significantly higher probability of reverse transcription and real-time polymerase chain amplification (RT-PCR) positivity compared with men. Our analysis shows a noticeable seasonal tendency, with an increase of RT-PCR positivity in summer, when positive cases are almost twice as frequent as in other seasons (OR=1.98; 95% CI = 1.77-2.22; p=0.0001). However, autumn appears to influence antigen test sensitivity, with a positive antigen test in autumn around ten times higher than in other seasons of the year (OR=9.90; 95% CI = 1.16-84.66; p=0.036). The logistic regression models revealed strong discriminatory power, with area under the curve values of 0.83 and 0.81 for the RT-PCR and antigen test, respectively. These values indicate an excellent ability to distinguish positive from negative individuals for both testing methods. Our study showed that seasonality strongly influences the spread of COVID-19 and the performance of diagnostic tests.