Newton 4/14 Update

Until April 8th Newton had been following a relatively smooth trajectory of initial post-social-distancing slowing of Covid-19 cases similar to that see in the US. On that day the Mayor announced that ~68 Covid-19 cases had been detected in a local nursing home, adding 39% to Newton’s then total of 178 cases.

On April 13th, Mayor Fuller reported “As of Sunday evening, Newton’s Health and Human Services Department (HHS) has received notice from the Massachusetts Department of Public Health (MDPH) of a total of 330 cases of COVID-19 among Newton residents. Of those 330 people, 45 percent [148] are individuals living in Newton nursing homes or assisted living facilities. This proportion has been relatively consistent over the past week.”.

In order to adapt to the sudden discovery of cases on April 8th, an estimated trajectory of those cases prior to April 8th was added to the reported totals assuming a growth rate of 20%.

Using this data set the 1st thing to assess is the pattern in case growth:

Although quite noisy, the pattern in Newton Covid-19 case growth shows a daily reduction of growth of 6.3% compared with 8.6% in the US. This likely reflects the difficulty in social distancing in nursing home environments. Using this projection of future case growth reduction forecasts the following case curves on logarithmic and linear scales:

[updated 4/17]

With this model, Newton cases currently plateau at 850, or about 1% of the city’s population. If distancing can be made more effective in the nursing home population of patients and caregivers, the rate of growth slowing likely can be increases and the ultimate case growth reduced to follow the US model to a plateau of 600 cases.

Here is a projection of how that looks on a daily basis using the average of the US and Newton projections as the center line and uncertainty estimated as 2x the recent error added to the high and low projections respectively. This projects we could get down to 0 case reports/day as soon as May 13th and/or have them persist as late as June 16th.

Based on general trends in the US case fatality rate compared with other countries with different levels of testing, I’m estimating the actual infection rates are 4-10x reported, so this could translate to 4-10% of the city’s population.

Of course this all depends on avoiding further episodes of explosive case growth in the city’s community living homes.

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