Press Release

Community Measures Prevent Deaths During Pandemic, New Study Finds

School closures and other community strategies designed to reduce the possibility of spreading disease between people during an epidemic can save lives, particularly when the measures are used in combination and implemented soon after an outbreak begins in a community, according to a new study based on public records from the 1918-1919 influenza pandemic.

The findings, which are published in the Aug. 8 issue of the Journal of the American Medical Association, provide vital clues to help public officials planning for the next influenza pandemic and highlight the importance of community strategies. These strategies are particularly important because the intervention most likely to provide the best protection against pandemic influenza -- a vaccine -- is unlikely to be available at the outset of a pandemic. Community strategies that delay or reduce the impact of a pandemic (also called non-pharmaceutical interventions) may help reduce the spread of disease until a vaccine that is well-matched to the virus is available.

Scientists from the Centers for Disease Control and Prevention (CDC) and the University of Michigan Medical School's Center for the History of Medicine completed an exhaustive review of public records such as health department reports, U.S. Census mortality data and newspaper archives.

"Communities that were most successful during the 1918 pandemic quickly enacted a variety of measures," said Dr. Martin Cetron, director of CDC's Division of Global Migration and Quarantine and senior author of the study. "Those planning for the next pandemic need to carefully consider how to best use these strategies to protect people and decrease the potential impact of the next pandemic in their communities."

These strategies – voluntary isolation and quarantine, dismissal of students from school classrooms, and social distancing in the workplace and community – form the basis for CDC's guidelines for how American communities can empower themselves to confront the next influenza pandemic.

The JAMA study evaluated public health measures such as school closures and cancellation of public events, which 43 American cities took during the 1918 pandemic. The researchers sought to determine whether the timing, duration and combination of such measures impacted the city's death rate during the pandemic.

To determine the public health measures' effectiveness, the researchers analyzed each city's excess death rate - the number of pneumonia and influenza deaths in excess of the amount expected for the time period.

During a 24-week period in 1918-1919, more than 115,000 excess pneumonia and influenza deaths in the 43 cities were attributed to the pandemic. Cities that began interventions earlier had more success in decreasing excess deaths than those that implemented the measures later, regardless of how long the later interventions were in place or how they were executed.

In a telling example, New York City's early and sustained response, including isolation and quarantine and staggered business hours, resulted in the lowest excess death rate for any city on the East Coast during the time period reviewed. By contrast, Pittsburgh was well into its outbreak before implementing the interventions and experienced the highest excess death rate of any of the 43 cities.

"In a world faced by the threat of avian influenza or other novel strains of influenza, it is critical to determine if such costly and socially harsh measures as school closures and cancellation of public gatherings might not only lower death and case rates, but also delay the spread and allow time for the development and distribution of effective vaccines and antivirals," said Dr. Howard Markel, director of the University of Michigan Medical School's Center for the History of Medicine and lead author of the study. "We have demonstrated that these measures can have a real impact."

The interventions assessed fell into three major categories: school closures, bans on public gatherings and isolation of sick people and quarantine of their healthy household contacts. The most common approach was closing schools combined with banning public gatherings. All but three of the 43 communities closed schools during the 24-week period studied.

Influenza pandemics occur when a new influenza virus emerges to which most people have little or no immunity and the virus gains the ability to spread easily between people. The 1918 pandemic sickened about 20 percent of the world's population and caused an estimated 40 million deaths worldwide, about 550,000 of them in the United States.

For more information about community strategies for pandemic influenza, please http://www.pandemicflu.gov/plan/community/community_mitigation.pdf.

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES