Empirical Evidence for the Effectiveness of Movement Restrictions
There is a wide range of empirical data which pertains to the effectiveness of movement restrictions:
1. Historical evidence from other diseases.
Although smallpox had a high R0 and had rountinely ravaged the cities of Europe, it was unknown in the new world until Europeans brought it to the Americas on ships. It is likely that if such ships had never arrived, Native Americans would never have become infected with smallpox.
2. Historical evidence from the 1918 influenza pandemic.
The 1918 flu pandemic is one of the worst ever documented. At that time, there were no antibiotics, no antivirals and no vaccines. Yet, some communities completely escaped infections while others greatly decreased the number who died. Some examples:
A. Gunnison, Colorado.
From The Great Influenza by John M. Barry, p. 345-346:
Neither tiny nor isolated, Gunnison was a railroad town, a supply center for the west-central part of the state, the home of Western State Teachers College. In early October - far in advance of any cases of influenza - Gunnison and most neighboring towns issued a closing order and a ban on public gatherings. Then Gunnison decided to isolate itself entirely. Gunnison lawmen blocked all through roads. Train conductors warned all passengers that if they stepped foot on the platform in Gunnison to stretch their legs, they would be arrested and quarantined for five days. Two Nebraskans trying simply to drive through to a town in the next county ran the blockade and were thrown in jail.
[snip]
Gunnison escaped without a death.
See also: Influenza Digital Archive: Gunnison. The Center for the History of Medicine (CHM). University of Michigan Medical School.
B. American Samoa
From: McLeod et al. 2008
While it was in force, the maritime quarantine used by American Samoa from November 23, 1918, appeared to exclude pandemic influenza (2). Once influenza did reach this jurisdiction in 1920, no recorded deaths were attributed to influenza (in a population of ≈8,000) (8). In contrast, influenza spread rapidly through Western Samoa (now named Samoa). The impact was amplified by a lack of medical assistance and by food shortages in the area. Western Samoa had the worst death rate for any country or territory recorded in the 1918 pandemic, losing 19%–22% of its population (2).
C. Japan
From: Wikipedia
In Japan, 257,363 deaths were attributed to influenza by July 1919, giving an estimated 0.425% mortality rate, much lower than nearly all other Asian countries for which data are available. The Japanese government severely restricted maritime travel to and from the home islands when the pandemic struck.
3. Yearly influenza epidemics follow predictable paths from Asia to other countries via international airports.
Two recent papers suggest that human influenza originates in tropical Asia and then spreads to the other continents (Rambaut et al. 2008; Russell et al. 2008). The authors of these papers reached their conclusions based an extensive analysis of influenza sequences. The pattern of spread follows international air travel from Asia with infections of Europe and North America preceding infections of South America.
4. Shutting down US airports for several days after 9/11 delayed the peak of influenza infections in the US by 13 days.
Analysis of patterns of arrival and spread of yearly influenza demonstrated a strong correlation between international travel to the US and the peak level of influenza deaths in the US (Brownstein et al. 2006). Further, the closure of US airports for just a few days after 9/11 had a dramatic effect on the peak of influenza infections in the US. A delay of 13 days was observed in the US while no delay was observed in France where there were no travel restrictions.
References
McLeod et al. (2008) Protective Effect of Maritime Quarantine in South Pacific Jurisdictions, 1918–19 Influenza Pandemic. Emerg Infect Dis. March.
The Center for the History of Medicine (CHM). University of Michigan Medical School. The 1918-1920 Influenza Pandemic Escape Community Digital Document Archive.
Brownstein et al. (2006) Empirical Evidence for the Effect of Airline Travel on Inter-Regional Influenza Spread in the United States. PLoS Medicine. 3:e401.
Rambaut et al. (2008) The genomic and epidemiological dynamics of human influenza A virus. Nature.
Russell et al. (2008) The Global Circulation of Seasonal Influenza A (H3N2) Viruses. Science.
Rice, Geoffrey W.; Edwina Palmer (1993). "Pandemic Influenza in Japan, 1918-1919: Mortality Patterns and Official Responses". Journal of Japanese Studies 19: 389–420.