Volume 13, Number 9—September 2007
Research
Frequent Travelers and Rate of Spread of Epidemics
T. Déirdre Hollingsworth*
, Neil M. Ferguson*, and Roy M. Anderson*
, Neil M. Ferguson*, and Roy M. Anderson*Table 1
Parameter descriptions and values of epidemiologic model that simulates exportation of cases from SARS-like and influenza-like epidemics*
| Description | Parameter | Value (reference) |
|
|---|---|---|---|
| SARS | Influenza | ||
| Infection | |||
| Basic reproductive number | R0 | 2.5 (13) | 1.8 (14) |
| Latent period, d | TL | 4 (13) | 1.5 (14) |
| Infectious period, d | TI | 10 (13) | 1.1 (14) |
| Generation time, d | Tg = TL + TI | 14 | 2.6 |
| Epidemic doubling time, d | td = Tg / (R0 – 1) ln2 | 6.5 | 2.3 |
| International travel | |||
| Proportion of population who are high-frequency fliers | r | 0–0.5 | |
| Mixing between groups: φ = 1, random mixing; φ = 0, assortative mixing | φ | 0–1 | |
| Relative probability of flying of high-frequency fliers | f | 20 | |
| Mean probability of flying per day | ε | 0.005 (9) | |
| Probability of flying per day of high-frequency fliers | εH = f / 1 + (f – 1)r ε | 0.084 | |
| Probability of flying per day of low-frequency fliers | εL = 1 / 1 + (f – 1)r ε | 0.042 | |
| Probability of a case being exported | |||
| Homogeneous flying patterns | L = TLε | 0.02 | 0.008 |
| High-frequency fliers | lH = TLεH | 0.34 | 0.13 |
| Low-frequency fliers | lL = TLεL | 0.017 | 0.006 |
*SARS, severe acute respiratory syndrome.
