Ep 141 COVID-19 Part 5 Epidemiology and Prediction Models

Ashleigh Tuite infectious diseases mathematical modeler discusses factors predicting spread of SARS CoV-2, prediction models and flattening the curve of COVID-19. Is the COVID-19 virus likely to mutate? And if it does what are the most likely consequences? What do prediction models show in terms of how long this pandemic will last? Is there likely to be a 2nd peak?... Podcast production, sound design & editing by Anton Helman Written Summary and blog post by Anton Helman March, 2020 Cite this podcast as: Helman, A. Tuite, A. Episode 141 COVID-19 Part 5 - Epidemiology and Prediction Models. Emergency Medicine Cases. March, 2020. https://emergencymedicinecases.com/covid-19-epidemiology-prediction-models. Accessed [date] This podcast and blog post are based on Level C evidence - consensus and expert opinion. Examples of protocols, checklists and algorithms are for educational purposes and require modification for your particular needs as well as approval by your hospital before use in clinical practice. Key COVID-19 epidemiologic measurements Based on a systematic review published March 31st, current evidence suggests the following key COVID-19 epidemiologic measurements: * Doubling time: 3-7 days for the epidemic to double in size * Reproduction number - R0 (number of expected secondary cases arising from a single individual, a measure of the transmissibility of a disease): ranges from 1.9 to 6.5, probably between 2.0 and 3.0 (comparable to SARS-CoV, HINI outbreak and a bit more than seasonal influenza which is thought to be about 1.5) * Incubation period: 4-6 days (similar to SARS Co-V and MERS) * Serial interval: 4-8 days * Case fatality rate: ranged from 0.3% to 1.4% (outside China) * Duration of viral shedding: highly variable ranging from 8 to 37 days (viral RNA levels may be higher early after symptom onset) Johns Hopkins University interactive up-to-date map that tracks global transmission. Is SARS Co-V2 likely to mutate and become more virulent? Is there immunity post-infection? When SARS Co-V RNA virus replicates it is very error prone, so it does mutate, with estimated mutation rate of 1-2 per month (slower than influenza) however most mutations will be neutral and will not effect how the virus behaves. The virus will likely be relatively stable over the next few months and is unlikely to mutate into a more virulent and deadly virus, and we will likely be able to develop an effective vaccine within 15-18 months. Weak evidence suggests that some of the antibodies that are induced in those with COVID-19 are protective but it is not known whether all infected patients mount a protective immune response and how long a protective effect might last. According to the CDC it is unclear if there is immunity post-infection. Immunity post-infection is likely to occur but is unproven It is unclear how long immunity lasts as antigenic drift may occur Many expert virologists believe that recovered patients (including health care workers) will have at least short-term immunity Which preventative measures help the most to curb transmission of SARS-CoV2? One of the drivers of the Reproduction number - R0 is the number of contacts people in the region each have per day. A combined strategy of workplace distancing, quarantine of exposed individuals (and less so) school closures and airport screening, seem to be highly effective at containing spread, however the effectiveness of these control measures could be curtailed by a significant portion of asymptomatic patients (17.9%), and pre-symptomatic transmission (12.1%). Responsive social distancing plan According to University of Toronto mathematical pred...