Id |
Subject |
Object |
Predicate |
Lexical cue |
T46 |
0-4 |
Sentence |
denotes |
Data |
T47 |
5-228 |
Sentence |
denotes |
We fit the physical distancing model to case-count data from British Columbia from March 1, 2020 (when a total of eight cases had been detected in the province) to April 11, 2020 at which time 1445 cases had been confirmed. |
T48 |
229-418 |
Sentence |
denotes |
These data are available in press releases from the BC Centre for Disease Control (BCCDC) [10], from the public data dashboard [17], and from the code repository associated with this paper. |
T49 |
419-483 |
Sentence |
denotes |
Testing procedures were adapted over the course of the outbreak. |
T50 |
484-724 |
Sentence |
denotes |
In particular, lab testing criteria were changed on March 16 to focus on hospitalized patients, healthcare workers, long-term care facility residents/staff, and those people part of an existing cluster and experiencing respiratory symptoms. |
T51 |
725-849 |
Sentence |
denotes |
This led to high variability in case counts in the surrounding days with some large jumps in the number of identified cases. |
T52 |
850-1046 |
Sentence |
denotes |
We accounted for this in the model by adjusting the testing fraction ψr to accommodate widening the testing pool and thereby increasing the fraction of infected individuals being tested (Table 1). |
T53 |
1047-1100 |
Sentence |
denotes |
There was also variability in the daily testing rate. |
T54 |
1101-1230 |
Sentence |
denotes |
During March, the daily number of completed tests ranged from approximately 100 to 3500, and did not strictly increase over time. |
T55 |
1231-1384 |
Sentence |
denotes |
Table 1 Values and sources for British Columbia parameterization of the model (see Supplemental Methods and Table B in S1 Text for other jurisdictions). |
T56 |
1385-1527 |
Sentence |
denotes |
The duration of the infectious period is shorter than the duration of severe illness, accounting for self-isolation and less severe illnesses. |
T57 |
1528-1677 |
Sentence |
denotes |
The quarantine parameter q reflects approximately 1/5 of severe cases either ceasing to transmit due to hospitalization or completely self-isolating. |
T58 |
1678-1817 |
Sentence |
denotes |
The model depends on the combination ur/(ur + ud), the fraction engaged in physical distancing, estimated from the survey data cited above. |
T59 |
1818-1969 |
Sentence |
denotes |
The testing patterns have changed over time, with laboratories increasing the numbers of tests on approximately March 14 (motivating our change in ψr). |
T60 |
1970-2027 |
Sentence |
denotes |
Symbol Definition Specified/fitted value Justification |
T61 |
2028-2063 |
Sentence |
denotes |
N Population size 5,100,000 [23] |
T62 |
2064-2123 |
Sentence |
denotes |
D Mean duration of the infectious period 5 days [24, 25] |
T63 |
2124-2187 |
Sentence |
denotes |
k 1 (time to infectiousness)−1 (E1 to E2) 0.2 days−1 [26–28] |
T64 |
2188-2274 |
Sentence |
denotes |
k 2 (time period of pre-symptomatic transmissibility)−1 (E2 to I) 1 days−1 [27, 28] |
T65 |
2275-2305 |
Sentence |
denotes |
q Quarantine rate 0.05 [29] |
T66 |
2306-2366 |
Sentence |
denotes |
u d Rate of people moving to physical distancing 0.1 [20] |
T67 |
2367-2434 |
Sentence |
denotes |
u r Rate of people returning from physical distancing 0.02 [20] |
T68 |
2435-2532 |
Sentence |
denotes |
ψ r Proportion of anticipated cases on day r that are tested and reported 0.1 Before March 14 |
T69 |
2533-2559 |
Sentence |
denotes |
0.3 On and after March 14 |
T70 |
2560-2669 |
Sentence |
denotes |
Shape Weibull parameter in delay-to-reporting distribution 1.73 (1.60–1.86 95% CI) Fit to data from Fig 1B |
T71 |
2670-2780 |
Sentence |
denotes |
Scale Weibull parameter in delay-to-reporting distribution 9.85 (9.30–10.46 95% CI) Fit to data from Fig 1B |
T72 |
2781-2862 |
Sentence |
denotes |
R 0b Basic reproductive number 2.95 (2.88–3.02 95% CI) Fit to data from Fig 1C |
T73 |
2863-2973 |
Sentence |
denotes |
f 2 Fraction of normal contacts during physical distancing 0.22 (0.08– 0.36 95% CI) Fit to data from Fig 1C |
T74 |
2974-3187 |
Sentence |
denotes |
ϕ Inverse dispersion from negative binomial (NB2) observation model 6.86 (3.39–12.37 95% CI) Fit to data from Fig 1C For some confirmed cases in BC, estimates of the date of symptom onset are available (Fig 1). |
T75 |
3188-3300 |
Sentence |
denotes |
We used the delays between symptom onset and cases being reported to parameterize the physical distancing model. |
T76 |
3301-3443 |
Sentence |
denotes |
In this case-specific data set there were only seven cases reported before February 29, and a decline in reported cases after April 2 (Fig 1). |
T77 |
3444-3590 |
Sentence |
denotes |
Therefore we used only the 535 cases in the case-specific data that were reported between these dates to parameterize the delay part of the model. |
T78 |
3591-3785 |
Sentence |
denotes |
For California (CA), New York (NY), and Florida (FL) we used reported case and testing data from The COVID Tracking Project, and assumed a BC-like delay between symptom onset and case reporting. |
T79 |
3786-3873 |
Sentence |
denotes |
For New Zealand (NZ) we used reported cases from the NZ Ministry of Health [18], and A. |
T80 |
3874-3887 |
Sentence |
denotes |
Lustig and M. |
T81 |
3888-4067 |
Sentence |
denotes |
Plank (pers. comm.) fit the delay distribution to NZ case-reporting data using our package [19], since these data are not publicly available (see Supplemental Methods in S1 Text). |
T82 |
4068-4145 |
Sentence |
denotes |
For our main analysis with BC, we fit our model to data until April 11, 2020. |
T83 |
4146-4389 |
Sentence |
denotes |
When demonstrating the application of our model to other jurisdictions, we included data until May 6 or 7, 2020, the date we completed this portion of the analysis and before these jurisdictions had begun relaxing physical distancing measures. |
T84 |
4390-4679 |
Sentence |
denotes |
An outbreak at a poultry plant in BC, combined with an expansion of testing in mid April, meant that in order to extend the BC model to May 6 or 7, we would have had to introduce changes to the methodology that would not be straightforward and would not be possible in other jurisdictions. |
T85 |
4680-4877 |
Sentence |
denotes |
These include, for example, modelling the poultry workforce’s interventions and contacts and the links between the outbreak and general community transmission, in concert with differential testing. |
T86 |
4878-4942 |
Sentence |
denotes |
We therefore limited the data used for the BC model to April 11. |
T87 |
4943-5147 |
Sentence |
denotes |
We motivated the structure of our model based on a survey conducted by the Angus Reid Institute to examine how physical distancing measures changed behaviour in Canada (March 20–23, 2020; n = 1664; [20]). |
T88 |
5148-5349 |
Sentence |
denotes |
Responses indicated that there was a subset of the population believing that the response to the COVID-19 epidemic was “overblown”, who were less willing than others to engage in distancing behaviours. |
T89 |
5350-5528 |
Sentence |
denotes |
This motivated treating the distancing and non-distancing compartments of our model separately and assuming that ∼80% of individuals were able and willing to physically distance. |
T90 |
5529-5714 |
Sentence |
denotes |
We used the timing of known government interventions to inform the timing of behavioural changes, and verified these dates against publicly available mobility data for each region [21]. |