Table 1.
Assumed values for input parameters of the arithmetic model as intended to be representative of COVID-19 transmission and successful epidemic containment in the United Republic of Tanzania (Fig. 1). A detailed formal description of how the model calculations are made, the underlying assumptions are provided in the online methodological supplement to this paper.
| Input parameter description | Assumed value | References |
|---|---|---|
| Basic reproductive number (Average number of new infections arising from a single existing infection over its full duration if allowed to do so in a fully susceptible, immunologically naïve population in the absence of any control measures) | 4.0 | Anastassopoulou, Russo, Tsakris, & Siettos, 2020; Chen et al., 2020; Choi & Ki, 2020; Kucharski et al., 2020; Mizumoto, Kagaya, & Chowell, 2020; Read, Bridgen, Cummings, Ho, & Jewell, 2020; Roosa et al., 2020b, 2020a; Sanche et al., 2020; Shim, Tariq, Choi, Lee, & Chowell, 2020; B. Tang et al., 2020, Tang et al., 2020, Tang et al., 2020, X.; Wang et al., 2020, Wang et al., 2020; Wu et al., 2020 |
| Duration of infection (Average number of weeks an infection lasts in a human before it is eliminated by the immune system). | 3 | Hu et al., 2020; Kam et al., 2020; Linton et al., 2020; Rothe et al., 2020; A.; Tang, Tong, et al., 2020; Xing et al., 2020; Zou et al., 2020 |
| Human population size | 57 million | National Bureau of Statistics & Ministry of Finance and Planning Dar es Salaam and the Office of the Chief Government Statistician & Ministry of Finance and Planning Zanzibar, 2018 |
| Baseline incidence of unrelated similar symptoms (Proportion of population per week experiencing similar symptoms to COVID-19 but caused by other common pathogens like the common cold, influenza, malaria, etc) | 1% | BMJ Best Practice, 2020; Ghinai et al., 2020 |
| Initial importation rate (Number of new primary cases arriving into the country each week) | 5 | Assumed |
| Time to initiation of importation containment intervention at border posts, airports and ports of entry (Number of weeks since the first imported cases before inbound travellers to the country are isolated on arrival) | 2 | Assumed |
| Time to initiation of lock-down intervention (Number of weeks since the first imported cases before population-wide restrictions are introduced to prevent personal exposure behaviours) | 5 | Assumed |
| Duration of lock-down intervention (Number of weeks since initiation of population-wide restrictions to prevent personal exposure behaviours until these restrictions are lifted) | 15 | Assumed |
| Asymptomatic proportion of cases (Proportion of all cases who lack, don’t notice or don’t report any overt symptoms associated with the infection) | 50% | Gostic, Gomez, Mummah, Kucharski, & Lloyd-Smith, 2020; Li et al., 2020; Mizumoto et al., 2020; Nishiura et al., 2020, Nishiura et al., 2020; Nishiura, Linton, & Akhmetzhanov, 2020; Qiu et al., 2020; Su et al., 2020; C.; Wang, Liu, et al., 2020 |
| Proportion of symptomatic cases which are clinically severe (Percentage of all cases exhibiting and reporting with severe symptoms, all of whom are assumed to be tested unless the limits of testing capacity are exceeded) | 20% | Guan et al., 2020; C.; Wang, Liu, et al., 2020 |
| Proportion of mild and severe symptomatic cases requiring critical care (Percentage of all cases exhibiting and reporting with any mild or severe symptoms who need intensive care, which can also be described as ) | 4% | Guan et al., 2020; C.; Wang, Liu, et al., 2020; Yang et al., 2020 |
| Intensive care unit (ICU) capacity (Maximum achievable percentage of the population that could be admitted to an ICU at a given time, allowing for maximum emergency expansion of capacity at short notice) | 0.0002% | Engdahl Mtango et al. (2019) |
| Case fatality rate in ICUs (Percentage of cases needing intensive care who access it but die nevertheless) | 20% | Guan et al. (2020) |
| Case fatality rate outside ICUs (Percentage of cases needing intensive care but who cannot access it and die subsequently) | 50% | Assumed |
| Maximum achievable diagnostic testing rate (Percentage of entire population per week) | 0.02% | Assumed |
| Proportional containment of imported cases (Percentage of secondary cases arising from primary imported cases which are prevented by travel restrictions and isolation of inbound travellers from affected countries on arrival) | 100% | Assumed |
| Proportional containment of contact clusters of confirmed cases (Percentage of secondary cases arising from diagnostic-confirmed primary cases which are prevented by contact tracing and isolation) | 90% | Ghinai et al., 2020; Pung et al., 2020 |
| Proportional lock down effectiveness (Percentage reduction of exposure behaviours behaviours, eg. close personal contact, sharing venues, transport, goods and other objects, among the fraction of the population included in and compliant with the lock down interventions) | 90% | C. Wang, Liu, et al., 2020 |
| Proportional lock down coverage (Percentage of entire population included in and compliant with interventions to reduce exposure behaviours, inclusive of staying indoors, avoiding other people, wearing face masks, and frequent hand washing) | 90% | C. Wang, Liu, et al., 2020 |