ABSTRACT
Motivated by the novel coronavirus disease (COVID-19) pandemic, this paper aims to apply Gunter Stein's cautionary message of respecting the unstable to the problem of controlling the spread of an infectious disease. With this goal, we study the effect that delays and capacity constraints have in the test, trace, and isolate (TeTrIs) process, and how they impact its ability to prevent exponential disease spread. Our analysis highlights the critical importance of speed and scale in the TeTrIs process. Precisely, ensuring that the delay in the TeTrIs process is much smaller than the doubling time of the disease spread is necessary for achieving acceptable performance. Similarly, limited TeTrIs capacity introduces a threshold on the size of an outbreak beyond which the disease spreads almost like the uncontrolled case. Along the way, we provide numerical illustrations to highlight these points.
ABSTRACT
Background: There are some papers reporting a possible link between blood group type and susceptibility to SARS-CoV2 (COVID-19) infection and perhaps even with mortality. They describe a higher risk to develop COVID-19 in individuals with blood type A, whereas those with blood type O would have a lower susceptibility to COVID-19 infection. Aims: To describe the distribution of the blood groups among the COVID-19 patients admitted in our hospital during the worse pandemic months in our country (March to May) and their relation with survival. Methods: From March1st to May 31st1299 Covid-19 patients were admitted in our hospital (a 520-bed institution);a27% died. We had the blood group testing performed in297 out of the1299 patients. Those records were in our blood bank software (Delphy.) because of a previous transfusion or a transfusion during the COVID-19 hospitalization. We examined the ABO types among these patients and we compared this data with the frequency observed in the Spanish healthy population according to the Red Cross records of blood donors. Statistical study was performed using the Chi square test (χ2) and Kaplan-Meier survival curves, by SPSS software. Results: In the297 COVID-19 patients admitted in our Hospital with ABO blood type recorded, the 55.2% were men, 44.8% women;median age was 79 (21-103). We found a higher percentage of blood type A and a lower of O among the COVID-19 patients, compared with the prevalence of those blood groups in Spanish healthy population, but that difference was not statistically significant. Regarding survival curves among different blood groups, we found a decreased mortality in patients with O blood type (25.2%) compared with the rest of groups (34.5%). That difference was close to be statistically significant (p 0.08), showing a clear tendency that could be maybe significant with a bigger group of patients. Summary/Conclusion: The distribution of the blood group in COVID-19 admitted patients in our hospital is similar to data already published: a higher rate of COVID-19 infection in patients with blood type A and a lower rate of type O. We also found lower mortality in our patients with O blood type;with a special signification when we compare O with the rest of blood groups together. There are some literature describing that anti-A antibodies could be protective against COVID-19 infection;this could explain the tendency we found of better survival in patients with O blood type.