To City Council Members, Mayors, and City Managers of Champaign and Urbana
Recommendations to the Cities of Champaign and Urbana with respect to managing Covid-19
as the University of Illinois reopens for Fall 2020
From: Eric Jakobsson, Department of Molecular and Integrative Physiology and NCSA, UIUC
Santiago Nunez-Corrales, Graduate Program in Informatics, UIUC
Our Covid-19 modeling paper for Champaign-Urbana has been deposited to the repository
MedRxiv at
https://www.medrxiv.org/content/medrxiv/early/2020/07/25/2020.07.22.20159798.full.pdf
In addition to what has been posted at the preprint repository we have now modeled in more
detail the scenario facing the cities in the immediate future, as a large cohort of individuals come
to Champaign-Urbana bearing a significantly higher viral load than those who have been here up
to now. The results of this modeling lead us to suggest returning to Phase 3 constraints for bars
and restaurants for about 3 weeks from August 15 to September 8 until the University testing and
isolation has gone through its first cycle. Detailed results and explanation below. Would be glad
to discuss individually at 217 390 7024

The above graph contains our best calculation of the effects of moving Champaign-Urbana bars
and restaurants between Phase 3 and Phase 4 restrictions. The vertical axis is the fraction of

 the total population in C-U actively infected with Covid, which can’t be measured directly but is
inferred from measured positivity in tests and other factors in the population. Day 117 is
August 10, so the curves to the left of Day 117 represent the recent history (Phase 4) and what
the history would have been if we had never moved from Phase 3 to Phase 4. It is seen that the
difference is minimal. The first vertical line is at Day 122 (August 15), which is a popular movein date for people returning to campus. Beginning at about August 15, the curves turn distinctly
upwards. This is due to the influx into the community of the returning cohort, whom we
estimate to be carrying a population-normalized viral load characteristic of Illinois as a whole,
which is approximately nine times that in Champaign-Urbana. As the curves turn upwards, they
start to diverge, so a significant difference begins to be seen between the effects of Phase 3 and
Phase 4. The reason for this is the Phase 3 restrictions reduce contact between the incoming
cohort and everybody else. Between Day 130 (August 23, first day of classes, students and staff
must be tested to go on campus) and August 30 the rate of rise in infections slows down and
begins finally to turn downwards. The slowing and reversal is due to the completion of the first
round of comprehensive testing and isolation of positives of University students and staff. By
August 30 the testing and isolation regimen is beginning to win the battle against the imported
viral load in the returning cohort.
The widest gap between Phase 3 and Phase 4 is on Day 137 (August 30), at which point under
the Phase 4 regimen approximately 2.7% of the cities’ population is infected while under a
reversion to phase 3 just 2.1% is infected. After this date both the Phase 3 and Phase 4 curves
decline and move closer together. They have come together by Day 145 (September 8) which
implies that at that point return to Phase 4 would be appropriate, so the total duration of
return to Phase 3, should the cities decide to do that, would be about three weeks.
The difference between the peak infective states of the population between 2.7% and 2.1%,
0.6%, amounts to about 800 more people who will be infected if Phase 4 is maintained. We can
reasonably estimate that 10%, or approximately 80 of those individuals, will require
hospitalization. It is estimated one-half-of one per cent of those infected with Covid-19 die.
That would amount to 4 deaths to be attributed to a decision to maintain Phase 4 rather than
temporarily return to Phase 3