ABSTRACT
The susceptible-infectious-removed (SIR) model offers the simplest framework to study transmission dynamics of COVID-19, however, it does not factor in its early depleting trend observed during a lockdown. We modified the SIR model to specifically simulate the early depleting transmission dynamics of COVID-19 to better predict its temporal trend in Malaysia. The classical SIR model was fitted to observed total (I total), active (I), and removed (R) cases of COVID-19 before lockdown to estimate the basic reproduction number. Next, the model was modified with a partial time-varying force of infection, given by a proportionally depleting transmission coefficient, βt, and a fractional term, z. The modified SIR model was then fitted to observed data over 6 weeks during the lockdown. Model fitting and projection were validated using the mean absolute percent error (MAPE). The transmission dynamics of COVID-19 was interrupted immediately by the lockdown. The modified SIR model projected the depleting temporal trends with lowest MAPE for I total, followed by I, I daily, and R. During lockdown, the dynamics of COVID-19 depleted at a rate of 4·7% each day with a decreased capacity of 40%. For 7–day and 14–day projections, the modified SIR model accurately predicted I total, I, and R. The depleting transmission dynamics for COVID-19 during lockdown can be accurately captured by time-varying SIR model. Projection generated based on observed data is useful for future planning and control of COVID-19.
Subject(s)
COVID-19ABSTRACT
IntroductionHealthcare workers (HCW) are presumed to be at increased risk of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection due to occupational exposure to infected patients. We aim to determine the prevalence of anti-SARS-CoV-2 antibodies among asymptomatic HCW.MethodsWe prospectively recruited HCW from the National Public Health Laboratory and two COVID-19 designated public hospitals in Klang Valley, Malaysia between April 13th and May 12th, 2020. Quota sampling was applied to ensure adequate representation of the HCW involved in provision of care for patients directly and indirectly. All participants had worked in the respective healthcare facility for at least 30 days prior study enrollment. HCW who were previously confirmed with COVID-19 infection or listed as “patient under investigation” were excluded. A self-administered questionnaire was used to capture sociodemographic information, history of contact with COVID-19 cases within the past month, clinical signs and symptoms and adherence to universal precautions. Blood samples were taken to test for anti-SARS-CoV-2 antibodies by surrogate virus neutralization test.ResultsA total of 400 HCW were recruited, comprising 154 (38.5%) nurses, 103 (25.8%) medical doctors, 47 (11.8%) laboratory technologists and others (23.9%). The mean age was 35±7.8 years, with females predominant (74%). A majority (68.9%) reported direct contact with COVID-19 patients, body fluids of COVID-19 patients and/or contaminated objects and surfaces in the past month within their respective workplaces. Nearly all claimed to adhere to personal protection equipment (PPE) guidelines (97%-100% adherence) and hand hygiene practice (91%-96% adherence). None (95% CI: 0, 0.0095) of the participants had anti-SARS-CoV-2 antibodies detected, despite 135 (33.8%) reporting respiratory symptoms one month prior to study recruitment. One hundred and fifteen (29%) participants claimed to have contact with known COVID-19 persons outside of the workplace.ConclusionOur finding of zero seroprevalence among asymptomatic HCW suggests a low risk of asymptomatic COVID-19 infection in our healthcare setting; which is at expected levels for a country with an incidence of 26 per 100,000. The adequacy of PPE equipment and strict adherence to infection prevention and control measures offers considerable protection during contact with COVID-19 cases and should be ensured to prevent future nosocomial transmission.