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day 0 is mid-Feb 2020, day 150 is thus mid-July
the timing of the peak is very sensitive to the duration a patient is likely to be infectious or the incubation period, and less sensitive to reductions in R0
some things to note with this calculator:
it is really designed to examine community spread and not cases brought in from outside the region
it would appear that given it displays calculated numbers of infected persons rather than tested confirmed cases, one should probably use the true fatality rate of around 0.7% rather than case fatality rates, and thus the hospitality rates should also be reduced to have the unconfirmed community cases added to the denominator and thus hospitalization rates should perhaps be reduced from 20% down to around 3-5%
unless you untick the display fatalities option, the chart of those in hospital is actually in ADDITION to fatalities to date so you need to look at the value on the left legend to determine how many are in hospital, not the Y axis value.
for a suburban region of population 750,000, incubation period 5 days, infectious period 6 days, CFR 0.7%, time to hospitalization 5 days, hospitalization rate 4%, hosp. LOS 15 days, time to death 18 days, initial R0 of 2.2:
if no social distancing measures and R0 remains at 2.2:
peak hospitalizations will occur at day 130 with around 6,400 in hospital although there are only around 1000 actual beds and deaths at this time would be around 2,100 with 70 deaths per day at CFR of 0.7% but given the health services would be overwhelmed, CFR may well be 5 times this much as is the Italian scenario. Hospitalized cases would continue for about 250 days as herd immunity exceeds 80% and total fatalities would reach over 4,000 if hospital capacity was able to meet demand but the realities are that fatalities would probably be 5 times this much.
if social distancing reduces R0 to 1.6:
peak hospitalizations will occur at day 180 with around 3,200 in hospital although there are only around 1000 actual beds and deaths at this time would be around 1,800 with 33 deaths per day at CFR of 0.7% but given the health services would be overwhelmed, CFR may well be 3-5 times this much as is the Italian scenario. Hospitalized cases would continue for about 1 year and presumably social distancing will need to be almost as long. Total fatalities would reach over 3,000 but may be 3-5x this much if system is over-whelmed.
if social distancing reduces R0 to 1.2:
peak hospitalizations will occur at day 270 with around 700 in hospital which is now manageable while deaths at this time would be around 840 with 7 deaths per day. Hospitalized cases would continue for almost 2 years and presumably social distancing will need to be almost as long. Total fatalities would reach over 1,600.
if extreme social distancing reduces R0 to 0.8:
peak hospitalizations will occur at day 25 after the reduction to R0 of 0.8 with around 45 in hospital and deaths at this time would be around 14, HOWEVER, borders would need to remain closed until a vaccine is available otherwise it will start all over again. Hospitalized cases would continue for about 1 year and presumably extreme social distancing will need to be almost as long. Total fatalities would be around 50.
scenario 2: July 2020 Stage 3 restrictions reduce R0 to 0.5
for Greater Melbourne population 4.5m, incubation period 5 days, infectious period 6 days, CFR 0.7%, time to hospitalization 7 days, hospitalization rate 6%, hosp. LOS 13 days, time to death 18 days, initial R0 of 1.8:
hospitalization peaks around 3 weeks after restrictions introduced at around 165 inpatients
after 2 months of restrictions:
inpatients fall to 50, deaths at around 70 and community infections at a potentially more controllable level of under 100-200
if restrictions then lifted and outbreaks not kept under control, risk of return to July levels very rapidly.
had stage 3 restrictions not been put in place and R0 was 1.8:
by 2 months: 50,000 infectious, peak hospitalisation of 33,000 inpatients well above capacity at 18wk mark and by 200 day mark, herd immunity obtained but with perhaps 350,000 deaths across Greater Melbourne as case fatality rate would become closer to that seen in northern Italy with an overwhelmed health system.
scenario 3: Aug 2020 Stage 4 restrictions only reduce R0 to 2.15
for Greater Melbourne population 4.5m, incubation period 5 days, infectious period 6 days, CFR 1.15%, time to hospitalization 7 days, hospitalization rate 4.7%, hosp. LOS 16 days, time to death 18 days, initial R0 of 2.5 (June 2020):
On 10th July (day 45 of 2nd wave), there were 1000 active cases
On 26th July there were over 4,000 active cases, 228 in hospital, 70 deaths this would fit with the model of R0 = 2.15 for the period 10th-26th July!
if this R0 were to continue at 2.15 for 10% of Melbourne's population who are less able to comply while 90% of the population comply strictly and do not get infected in this wave:
by 9th August, we would hit over 11,000 active cases, 40 hospital admissions a day with over 550 inpatients and deaths increasing to 11 per day for a total of over 130
by early Sept at day 100, we would hit over 45,000 active cases, 160 hospital admissions a day with over 3,000 inpatients and deaths increasing to 50 per day for a total of well over 800
by late Sept at day 126 hospital inpatients would peak at over 45,000 active cases, with over 6,000 inpatients and deaths increasing to 80 per day for a total of around 3,000 (probably a lot more as the hospital systems are now over-whelmed)
by Dec this wave would have almost ended as long as the 90% do not stop complying while there are infectious cases whilst 10% of Melbourne's population would have been infected with over 5,000 dying.