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.

In response to an intensifying outbreak in the United States and internationally caused by a new influenza virus of swine origin, the World Health Organization raised the worldwide pandemic alert level to Phase 5 on April 29, 2009. A Phase 5 alert is a “strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.”

The United States Government has declared a public health emergency in the United States. CDC’s response goals are to reduce transmission and illness severity, and provide information to help health care providers, public health officials and the public address the challenges posed by this emergency. CDC is issuing and updating interim guidance daily in response to the rapidly evolving situation. CDC’s Division of the Strategic National Stockpile (SNS) continues to send antiviral drugs, personal protective equipment, and respiratory protection devices to all 50 states and U.S. territories to help them respond to the outbreak. The swine influenza A (H1N1) virus is susceptible to the prescription antiviraldrugs oseltamivir and zanamivir. In addition, the Federal Government and manufacturers have begun the process of developing a vaccine against this new virus.

Past Daily Updates

• April 29, 2009
• April 28, 2009
• April 27, 2009
• April 26, 2009
• April 25, 2009
• April 24, 2009
• April 23, 2009