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Homeland Security

Flu Pandemic Mitigation - Social Distancing

Two ways of increasing social distance activity restrictions are to cancel events and close buildings or to restrict access to certain sites or buildings. These measures are sometimes called "focused measures to increase social distance." Depending on the situation, examples of cancellations and building closures might include: cancellation of public events (concerts, sports events, movies, plays) and closure of recreational facilities (community swimming pools, youth clubs, gymnasiums).

Closure of office buildings, stores, schools, and public transportation systems may be feasible community containment measures during a pandemic. All of these have significant impact on the community and workforce, however, and careful consideration should be focused on their potential effectiveness, how they can most effectively be implemented, and how to maintain critical supplies and infrastructure while limiting community interaction. For example, when public transportation is cancelled, other modes of transportation must be provided for emergency medical services and medical evaluation.

In general, providing information to domestic and international travellers (risks to avoid, symptoms to look for, when to seek care) is a better use of health resources than formal screening. Entry screening of travellers at international borders will incur considerable expense with a disproportionately small impact on international spread, although exit screening would be considered in some situations.

Although data is limited, school closures may be effective in decreasing spread of influenza and reducing the overall magnitude of disease in a community. In addition, the risk of infection and illness among children is likely to be decreased, which would be particularly important if the pandemic strain causes significant morbidity and mortality among children. Children are known to be efficient transmitters of seasonal influenza and other respiratory illnesses. Anecdotal reports suggest that community influenza outbreaks may be limited by closing schools. Results of mathematical modeling also suggest a reduction of overall disease, especially when schools are closed early in the outbreak. During a Pandemic Period, parents would be encouraged to consider child care arrangements that do not result in large gatherings of children outside the school setting.

There is some evidence that big gatherings of people encourage spread of flu, and measures to flatten the epidemic curve can helpful in easing the most intense pressure on health services. Limiting public gatherings can be an effective preventive measure for diseases that are transmitted through the air [unlike flu] - especially for diseases that are transmitted by individuals with no symptoms [such as flu]. Often, public health experts recommend limiting exposures to others-such as frequently occurs during influenza season. There is a big difference between recommending limited public gatherings and enforcing a more specific and uniform requirement. In making a decision to close gathering places, the impact on economy, education, and access to food / water / other necessities needs to be balanced with the ability to effectively protect the public through such means.

During the 1957-1958 pandemic, a WHO expert panel found that spread within some countries followed public gatherings, such as conferences and festivals. This panel also observed that in many countries the pandemic broke out first in camps, army units and schools; suggesting that the avoidance of crowding may be important in reducing the peak incidence of an epidemic.

During the first wave of the Asian influenza pandemic of 1957-1958, the highest attack rates were seen in school aged children. This has been attributed to their close contact in crowded settings. A published study found that during an influenza outbreak, school closures were associated with significant decreases in the incidence of viral respiratory diseases and health care utilization among children aged 6-12 years.

Given a pandemic strain causing significant morbidity and mortality in all age groups and the absence of a vaccine, the WHO consultation on priority public health interventions before and during an influenza pandemic concluded that authorities should seriously consider introducing population-wide measures to reduce the number of cases and deaths. These would include population-wide measures to reduce mixing of adults (furlough non-essential workers, close workplaces, discourage mass gatherings). Decisions can be guided by mathematical and economic modelling.

The Center for Biosecurity of University of Pittsburgh Medical Center [UPMC] argued that idea that the cancellation of public gatherings or the imposition of travel restrictions might limit the spread of disease are scientifically unfounded, and that presenting them has the potential to create false expectations about what can be accomplished by government officials and their proposed containment measures. The UK Government, for instance, has concluded that closing schools and other educational facilities would have a limited effect on the epidemic. There would be a major reduction in the numbers of students affected. On the other hand, there would be little reduction in the number of cases in the rest of the population. The UK Government concluded that there was little evidence that cancelling large public events would have any significant impact on the course of the epidemic.

Reverse Quarantine / Snow Days / Self-Shielding

Implementation of "snow days" - asking everyone to stay home - involves the entire community in a positive way, is acceptable to most people, and is relatively easy to implement. A "snow day" occurs when winter weather makes travel sufficiently hazardous that officials request that employees/students not report to work/school. In the context of a disease epidemic, a "snow day" would be declared to reduce public gatherings and limit contact among people. Snow days may be instituted for an initial 10-day period, with final decisions on duration based on an epidemiologic and social assessment of the situation. States and local authorities need to consider recommendations to the public for acquisition and storage of necessary provisions including type and quantity of supplies needed during snow days. Snow days can effectively reduce transmission without explicit activity restrictions (i.e., quarantine). Consideration would be given to personnel who maintain primary functions in the community (e.g., law enforcement personnel, transportation workers, utility workers [electricity, water, gas, telephone, sanitation]).

Compliance with snow days might be enhanced by "self-shielding" behavior (i.e., many people may stay home even in the absence of an official snow day ["reverse quarantine"]). Reverse quarantine involves the sequestration of people to reduce the likelihood of their exposure to the contagion. Short-term, voluntary home curfew is known as shelter-in-place or self-shielding. Self-shielding refers to self-imposed exclusion from infected persons or those perceived to be infected (e.g., by staying home from work or school during an epidemic). There has been essentially no discussion of these measures in the context of pandemic influenza.

Limiting public gatherings may also function as "reverse quarantine" in which individuals who have not been exposed to a communicable disease are asked to stay home or otherwise limit their exposure to others who may be carrying a communicable disease. This technique was said by some to be an important strategy in preventing transmission of influenza in 1918 and in the polio epidemic of the 1950s.

The self shielding construct was developed as a response to the threat of terrorist use of biological agents. The essential features are that people will remain at-home for a few days, or for a few weeks at most, and that the disease epidemic is thus aborted, prevented or minimized. Shielding can be undertaken by individuals, families or communities. It constitutes a positive action for the public, and engages them in plans and preparations before an incident. The shielding concept also offers advantages in insuring the continuation of some normalcy of finance, legal, and social institutions. The very planning to remain in the home and community will serve a positive mental health purpose during and following an incident. The period of incubation prior to development of an infectious stage of each disease and the period of disease will determine the required period for quarantine or the alternative of shielding. By one estimate this would range from 7 days for Anthrax to 28 days for Viral Hemorrhagic Fevers.

The purpose of shielding in responding to bio-terror attacks is to allow individuals, families and groups to undertake self-imposed exclusion from contact with the disease state, and infected persons, while encouraging those who are shielding to engage in appropriate routine activities. For those excluded from contact the important criteria will be to maintain a "shielded" status by ensuring no contact with anyone in the quarantine, isolation or asymptomatic groups, and that they self-monitor for signs of disease. In the case of smallpox this self-monitoring requires nothing more than monitoring their body temperature twice daily. If during the course of any 24 hour period the individual develops two successive fevers >101 F (38 C) they notify health department personnel and not have direct contact with other persons until they can be transported to an appropriate facility (i.e. Type C facility) for further evaluation.

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