2009 H1N1 Pandemic Timeline
In 2009, a new H1N1 influenza virus emerged, causing the first global flu pandemic in 40 years. Below is a timeline of major events that took place during the 2009 H1N1 pandemic.
- Timelineicon
April 15
- First human infection with new influenza A H1N1 virus detected in California.
- Timelineicon
April 17
- Second human infection with the new influenza A H1N1 virus detected in California about 130 miles away from first infection, with no known connection to previous patient.
- Timelineicon
April 18
- First novel 2009 H1N1 flu infections were reported by CDC to the World Health Organization (WHO) through the U.S. International Health Regulations Program.
- Timelineicon
April 21
- CDC publicly reported the first two U.S. infections with the new H1N1 virus.
- CDC began working to develop a candidate vaccine virus.
- Timelineicon
April 22
- CDC activated it’s Emergency Operations Center (EOC).
- Timelineicon
April 23
- Two additional human infections with 2009 H1N1 were detected in Texas, transforming the investigation into a multistate outbreak and response.
- Timelineicon
April 24
- CDC uploaded complete gene sequences of new H1N1 2009 virus to a publically-accessible international influenza database.
- Timelineicon
April 25
- The World Health Organization (WHO) declared a public health emergency of international concern.
- Timelineicon
April 26
- The United States Government declared 2009 H1N1 a Public Health Emergency of International Concern and CDC began releasing 25% of antiviral drugs needed to treat this new influenza virus from the federal stockpile.
- Timelineicon
April 27
- WHO Director-General raised the level of influenza pandemic alert from phase 3 to phase 4, based on data showing person-to-person spread and the ability of the virus to cause community-level outbreaks.
- Timelineicon
April 28
- The Food and Drug Administration (FDA) approved a new CDC test to detect 2009 H1N1 infections
- CDC issued the first CDC Interim Guidance on Closing Schools and Childcare Facilities, recommending a 7-day dismissal in affected schools and childcare facilities with laboratory-confirmed cases of influenza A H1N1 virus.
- Timelineicon
April 29
- WHO raised the level of influenza pandemic alert from phase 4 to phase 5, signaling that a pandemic was imminent, and requested all countries to immediately activate their pandemic preparedness plans and be on high alert for unusual outbreaks of influenza-like illness and severe pneumonia.
- Timelineicon
May
- 2009 H1N1 influenza summer activity peaked in the United States during May and June.
- Timelineicon
May 1
- Domestic and global shipments of new CDC test to detect 2009 H1N1 began.
- CDC updated the CDC Interim Guidance on Closing Schools and Childcare Facilities, recommending affected communities with lab-confirmed cases of influenza A H1N1 consider adopting school dismissal and childcare closing measures, including closing for up to 14 days depending on the extent and severity of influenza illness.
- Timelineicon
May 4
- CDC shifted from reporting confirmed cases of 2009 H1N1 to reporting both confirmed and probable cases of 2009 H1N1.
- Timelineicon
May 5
- Peak school dismissal day in the spring phase of the pandemic. 980 schools were dismissed, affecting 607,778 students.
- Timelineicon
May 6
- CDC distributed updated recommendations for the use of influenza antiviral medicines to provide guidance for clinicians in prescribing antiviral medicines for treatment and prevention (chemoprophylaxis) of 2009 H1N1 influenza.
- Timelineicon
May 8
- CDC issued an MMWR updating the 2009 H1N1 influenza situations in Mexico, the United States, and worldwide.
- Timelineicon
May 12
- CDC reported early data on 2009 H1N1 illness among pregnant women in an MMWR.
- Timelineicon
June 11
- The World Health Organization (WHO) declared a pandemic and raised the worldwide pandemic alert level to phase 6, which means the virus was spreading to other parts of the world.
- CDC held its first press conference with former CDC Director Thomas Frieden, MD, MPH. The press conference had 2,355 participants.
- Timelineicon
June 19
- All 50 states, the District of Colombia, Puerto Rico and the U.S. Virgin Islands had reported cases of 2009 H1N1 infection.
- By late-June, more than 30 summer camps in the U.S. had reported outbreaks of 2009 H1N1 influenza illness. CDC released guidance for day and residential camps to reduce spread of influenza.
- Timelineicon
June 25
- CDC estimated at least 1 million cases of 2009 H1N1 influenza had occurred in the United States.
- Timelineicon
Early July
- Reported cases of 2009 H1N1 nearly doubled since mid-June 2009.
- Three 2009 H1N1 influenza viruses that were resistant to the antiviral drug, oseltamivir, were detected in three countries.
- Timelineicon
July 10
- CDC reported findings in an MMWR that indicated a large prevalence of obesity in intensive care patients with confirmed 2009 H1N1 influenza infection.
- After mid-July, 2009 H1N1 influenza activity declined in most countries.
- Timelineicon
July 22
- Clinical trials testing the 2009 H1N1 flu vaccine began.
- Timelineicon
August
- Additional oseltamivir-resistant 2009 H1N1 viruses were detected by CDC.
- Timelineicon
August 3
- CDC School Dismissal Monitoring System (SDMS) activated.
- Timelineicon
August 19
- CDC Guidance for Businesses and accompanying toolkit posted to CDC.gov.
- Timelineicon
August 20
- CDC Guidance for Institutions of Higher Education (IHE) and accompanying toolkit posted to CDC.gov. Calls were conducted with Secretary Duncan and Sebelius to explain guidance. Press briefings followed.
- Second wave of 2009 H1N1 influenza activity began in the U.S.
- Timelineicon
August 30
- New reporting season for the 2009-2010 influenza season began.
- Timelineicon
September 1
- More than 1,000 test kits shipped to 120 domestic and 250 international laboratories in 140 countries since May 1, 2009.
- Timelineicon
September 3
- CDC published a study that analyzed data related to H1N1 influenza pediatric deaths reported to CDC from April to August 2009 in MMWR. Data showed 477 deaths with lab-confirmed 2009 H1N1 flu in the U.S. had been reported to CDC as of August 8, 2009.
- Timelineicon
September 10
- HHS secretary and CDC Director joined the National Foundation for Infectious Diseases (NFID) in a news conference to stress the importance of getting vaccinated for the upcoming influenza season.
- Timelineicon
September 15
- The FDA announced its approval of four 2009 H1N1 influenza vaccines.
- Timelineicon
September 30
- U.S. states placed first orders of 2009 H1N1 vaccine.
- Timelineicon
October
- National Influenza 2009 H1N1 vaccination campaign
- Timelineicon
October 5
- First doses of H1N1 vaccine were given in the U.S.
- Timelineicon
October 24
- Influenza activity reached its highest level in the reporting week ending October 24, 2009, with 48 of 50 states reported widespread activity.
- Timelineicon
Late October
- Second wave of H1N1 flu activity peaked in the U.S.
- Timelineicon
November 12
- CDC released its first estimates official estimates of 2009 H1N1 cases, hospitalization and deaths.
- Timelineicon
November 16
- FDA announced its approval of a fifth 2009 H1N1 vaccine.
- Timelineicon
November 23
- No school closures throughout United States; first time since 8/25/2009.
- Timelineicon
December
- Results of trials conducted among adults were published in December, and the data indicated that the immune response among vaccinated adults was excellent.
- Timelineicon
December 4
- CDC published preliminary safety results for the 2009 H1N1 vaccines for the first months of reports received through the U.S. Vaccine Adverse Event Reporting System (VAERSexternal icon).
- Timelineicon
December 18
- First 100 million doses of 2009 H1N1 vaccine were available for ordering.
- Timelineicon
Late December
- 2009 H1N1 vaccination had been opened up to anyone who wanted it.
2010
- Timelineicon
January
- Activity declined to levels below baseline, but persisted for several more months at lower levels.
- Timelineicon
January 10-16
- President of the United States proclaimed National Influenza Vaccination Week (NIVW) and encouraged all Americans to observe the week by getting vaccinated with the 2009 H1N1 flu vaccine.
- Timelineicon
February
- FDA’s VRBPAC selected 2009 H1N1 virus for inclusion in 2010-2011 seasonal flu vaccine
- Timelineicon
February 18
- WHO published recommendations for the composition of influenza virus vaccines for the upcoming Northern Hemisphere influenza season. Components included a 2009 H1N1-like virus.
- Timelineicon
April
- Between April 2009 and April 2010, CDC held 60 related media events – 39 press briefings and 22 telebriefings – reaching more than 35,000 participants.
- Timelineicon
August 11
- WHO announced the end of 2009 H1N1 influenza pandemic.