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Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

Interim CDC Guidance for Public Gatherings in Response to Human Infections with Novel Influenza A (H1N1)

September 23, 2009 2:00 PM EST

These recommendations are based on current information and are subject to change based on ongoing surveillance and risk assessment.


This document provides interim guidance for state, local, territorial, and tribal officials to use in developing recommendations for large public gatherings in their communities.

As used in this document, a large public gathering refers to an assembly or grouping of many people in one place.  Such gatherings can include college and university commencement exercises, church services, sporting events, concerts, social and cultural celebrations, weddings, conferences, and other similar activities attended by relatively large groups of people. This interim guidance does not attempt to define such events in terms of numbers of people in attendance; rather, the focus is on community situations in which crowding is likely to occur. In addition, these recommendations do not distinguish between public gatherings held indoors and those held outdoors, because differences in 2009 H1N1 flu transmission patterns in these two settings are not known.

In crowded settings, social distancing (that is, measures that increase the physical space between people and reduce their frequency of close contact) is difficult to maintain. Moreover, at public gathering events that are celebratory in nature (such as weddings, graduation ceremonies), participants frequently have social personal contact (like handshaking and hugging). As a result, there may be increased risk for spread of 2009 H1N1 rlu virus among attendees of such events and subsequent spread of illness in the community or in communities to where attendees return. The recommendations below are intended to reduce the spread of influenza infection in communities.

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Interim Recommendations

Decisions regarding large public gatherings in the context of this 2009 H1N1 flu outbreak should be made based on local influenza activity, evolving information about severity of illness from this virus, and identification of high risk groups, and other local considerations. However, given the current information on disease severity and spread, CDC recommends that:

  1. Persons with influenza-like illness (ILI) (i.e., fever with either cough or sore throat) should be advised to stay home until at least 24 hours after they are free of fever (100° F [37.8°C]), or signs of a fever without the use of fever-reducing medications.  This recommendation applies to camps, schools, businesses, mass gatherings, and other community settings where the majority of people are not at increased risk for influenza complications. This guidance does not apply to health care settings where the exclusion period should be continued for 7 days from symptom onset or until the resolution of symptoms, whichever is longer. See additional guidance for persons with ILI.
  2. Persons who are at high risk of complications from 2009 H1N1 flu infection (for example, persons with certain chronic medical conditions, children less than 5 years, persons 65 or older, and pregnant women) should consider their risk of exposure to novel influenza if they attend public gatherings in communities where novel influenza A virus is circulating. In communities with several reported cases of 2009 H1N1 Fflu virus infection, persons who are at risk of complications from influenza should consider staying away from public gatherings.
  3. All persons should be reminded to use appropriate respiratory and hand hygiene precautions.
  4. Based on currently available information, for non-healthcare settings where frequent exposures to persons with 2009 H1N1 flu are unlikely, masks and respirators are not recommended.

Large public gatherings offer a good opportunity for public health officials and event organizers to deliver key educational messages about measures attendees can take to help reduce the spread of 2009 H1N1 flu infection. Event organizers should consider communicating to attendees about the need to remain home if ill and to use good hygiene practices while at the event. Such information may be communicated through a variety of means such as letters, newspaper notices, public service announcements, Web site postings, and text messages. More information is available.

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Additional Measures

Other measures can be used by event organizers to help reduce the risk for 2009 H1N1 flu infection. The feasibility of their use may vary depending on the type and setting of the event.

  • Make widely available at the event hand washing facilities with soap and running water, hand sanitizer, and tissues.
  • Provide on-site medical assessment and care for persons with ILI.
  • Provide alternative options and venues for participation (e.g., remote Web-based viewing sites) and simultaneously reduce crowding.

These recommendations are subject to change as more information about 2009 H1N1 flu becomes available.

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