Interim CDC Guidance for Mitigation in Response to Human Infections with Swine Influenza (H1N1) Virus

This document provides interim planning guidance that focuses on several nonpharmaceutical measures that might be useful during this outbreak of swine influenza A (H1N1) virus aimed at reducing disease transmission and associated morbidity and mortality.

Human cases of swine influenza A (H1N1) virus infection have been identified in several states and in other countries. This is a novel influenza A virus that has not been identified in people before, and human-to-human transmission of the virus appears to be ongoing.


Unlike the experience in Mexico, the United States is currently observing a less severe clinical spectrum of disease with infection by the identical virus strain. In Mexico, many patients have experienced rapidly progressive pneumonia, respiratory failure requiring mechanical ventilation and acute respiratory distress syndrome (ARDS). Therefore, the experience of these two countries has been markedly different to date. Getting better information to explain these differences is a high priority for the ongoing investigation.

The previously published United States government guidance on community mitigation relies on knowledge of the Pandemic Severity Index (PSI) to characterize the severity of a pandemic and identify the recommendations for specific interventions that communities may use for a given level of severity, and suggests when these measures should be started and how long they should be used.

The substantial difference in the severity of the illness associated with infections from the same virus, the relatively low number of cases detected in the United States, and insufficient epidemiologic and clinical data to ascribe a PSI, present a formidable challenge in terms of assessing the threat posed by this novel influenza A virus until additional epidemiologic and virologic information is learned.

Novel influenza A virus infections in humans, including swine influenza A (H1N1) virus, represent a pandemic threat. Recognizing the historical precedent for the emergence of a pandemic influenza virus which could have waves of disease with different morbidity and mortality and epidemiologic profiles, public health departments in the United States must remain vigilant.

It is prudent for communities to act in the absence of sufficient data to protect their citizens and take advantage of a narrow window of opportunity for intervention. CDC recommends that affected states with at least one laboratory-confirmed case of swine influenza A (H1N1) virus infection consider activating community mitigation interventions for affected communities. As public health officials in the United States learn more about this emerging virus, updated guidance will be issued.



When Human Infection with Swine Influenza A (H1N1) Virus is Confirmed in a Community

  • Persons who develop influenza-like-illness (ILI) (fever with either cough or sore throat) should be strongly encouraged to self-isolate in their home for 7 days after the onset of illness or at least 24 hours after symptoms have resolved, whichever is longer. Persons who experience ILI and wish to seek medical care should contact their health care providers to report illness (by telephone or other remote means) before seeking care at a clinic, physician’s office, or hospital. Persons who have difficulty breathing or shortness of breath or are believed to be severely ill should seek immediate medical attention.
  • If ill persons must go into the community (e.g., to seek medical care) they should wear a face mask to reduce the risk of spreading the virus in the community when they cough, sneeze, talk or breathe. If a face mask is unavailable, ill persons needing to go into the community should use a handkerchief or tissues to cover any coughing.
  • Persons in home isolation and their household members should be given infection control instructions: including frequent hand washing with soap and water. Use alcohol-based hand gels (containing at least 60% alcohol) when soap and water are not available and hands are not visibly dirty. When the ill person is within 6 feet of others at home, the ill person should wear a face mask if one is available and the ill person is able to tolerate wearing it.

Regarding Contacts

  • Contacts who are well should:

         1. remain home at the earliest sign of illness;
         2. minimize contact in the community to the extent possible;
         3. designate a single household family member as the ill person’s caregiver to minimize interactions with asymptomatic persons.

School Dismissal and Childcare Facility Closure

  • Dismissal of students should be strongly considered in schools with a confirmed or a suspected case epidemiologically linked to a confirmed case.
  • Decisions regarding broader school dismissal within these communities should be left to local authorities, taking into account the extent of ILI in the community.
  • If the school dismisses students or a childcare facility closes, they should also cancel all school or childcare related gatherings and encourage parents and students to avoid congregating outside of the school.
  • Schools and childcare facilities should dismiss students for a time period to be evaluated on an ongoing basis depending upon epidemiological findings.
  • Schools and childcare facilities should consult with their local or state health departments for guidance on reopening. If no additional confirmed or suspected cases are identified among students (or school-based personnel) for a period of 7 days, schools may consider reopening.
  • Schools and childcare facilities in unaffected areas should begin to prepare for the possibility of school dismissal or childcare facility closure. This includes asking teachers, parents and officials in charge of critical school-associated programs (such as meal services) to make contingency plans.

Other Social Distancing Interventions

  • Large gatherings linked to settings or institutions with laboratory-confirmed cases should be cancelled, for example a school event linked to a school with cases;other large gatherings in the community may not need to be cancelled at this time.
  • Additional social distancing measures are currently not recommended.
  • Persons with underlying medical conditions who are at high risk for complications of influenza may wish to consider avoiding large gatherings.

These recommendations are subject to change as additional epidemiological and clinical data become available.

The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.

Since it was founded in 1946 to help control malaria, CDC has remained at the forefront of public health efforts to prevent and control infectious and chronic diseases, injuries, workplace hazards, disabilities and environmental health threats.