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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.

Novel H1N1 Flu Situation Update
May 21, 2009, 11:00 AM ET

Map: Weekly Influenza Activity Estimates, Including Novel H1N1 Flu

FluView, Week Ending May 09, 2009. Weekly Influenza Surveillance Report Prepared by the Influenza Division. Weekly Influenza Activity Estimate Reported by State and Territorial Epidemiologists. Select this link for more detailed data.

For more details about the data in the map above, see the FluView Surveillance Report for the week ending May 9, 2009.

Table. U.S. Human Cases of H1N1 Flu Infection
(As of May 21, 2009, 11:00 AM ET)
States* Confirmed and Probable Cases Deaths
64 cases
1 deaths
488 cases
2 deaths
3 cases
0 deaths
553 cases
0 deaths
55 cases
0 deaths
59 cases
0 deaths
88 cases
0 deaths
122 cases
0 deaths
25 cases
0 deaths
30 cases
0 deaths
8 cases
0 deaths
794 cases
0 deaths
105 cases
0 deaths
71 cases
0 deaths
34 cases
0 deaths
20 cases
0 deaths
73 cases
0 deaths
9 cases
0 deaths
39 cases
0 deaths
175 cases
0 deaths
171 cases
0 deaths
39 cases
0 deaths
5 cases
0 deaths
20 cases
1 deaths
9 cases
0 deaths
28 cases
0 deaths
33 cases
0 deaths
New Hampshire
22 cases
0 deaths
New Jersey
22 cases
0 deaths
New Mexico
68 cases
0 deaths
New York
284 cases
1 deaths
North Carolina
12 cases
0 deaths
North Dakota
5 cases
0 deaths
13 cases
0 deaths
43 cases
0 deaths
94 cases
0 deaths
61 cases
0 deaths
Rhode Island
8 cases
0 deaths
South Carolina
36 cases
0 deaths
South Dakota
4 cases
0 deaths
86 cases
0 deaths
556 cases
3 deaths
116 cases
1 deaths
1 cases
0 deaths
23 cases
0 deaths
411 cases
1 death
Washington, D.C.
13 cases
0 deaths
766 cases
0 deaths
5,764 cases
9 deaths

*includes the District of Columbia

**one case is resident of KY but currently hospitalized in GA.

This table will be updated daily Monday-Friday at around 11 AM ET.

International Human Cases of Swine Flu Infection
See: World Health Organization.

NOTE: Because of daily reporting deadlines, the state totals reported by CDC may not always be consistent with those reported by state health departments. If there is a discrepancy between these two counts, data from the state health departments should be used as the most accurate number.

Summary of Situation

A New Influenza Virus

Novel influenza A (H1N1) is a new flu virus of swine origin that was first detected in April, 2009. The virus is infecting people and is spreading from person-to-person, sparking a growing outbreak of illness in the United States. An increasing number of cases are being reported internationally as well.

It’s thought that novel influenza A (H1N1) flu spreads in the same way that regular seasonal influenza viruses spread; mainly through the coughs and sneezes of people who are sick with the virus.

It’s uncertain at this time how severe this novel H1N1 outbreak will be in terms of illness and death compared with other influenza viruses. Because this is a new virus, most people will not have immunity to it, and illness may be more severe and widespread as a result. In addition, currently there is no vaccine to protect against this novel H1N1 virus. CDC anticipates that there will be more cases, more hospitalizations and more deaths associated with this new virus in the coming days and weeks.

Novel influenza A (H1N1) activity is now being detected through CDC’s routine influenza surveillance systems and reported weekly in FluView. CDC tracks U.S. influenza activity through multiple systems across five categories. The fact that novel H1N1 activity can now be monitored through seasonal surveillance systems is an indication that there are higher levels of influenza-like illness in the United States than is normal for this time of year. About half of all influenza viruses being detected are novel H1N1 viruses.

CDC Response

CDC continues to take aggressive action to respond to the outbreak. CDC’s response goals are to reduce the spread and severity of illness, and to provide information to help health care providers, public health officials and the public address the challenges posed by this new public health threat.

CDC is issuing updated interim guidance daily in response to the rapidly evolving situation.

Clinician Guidance

CDC has issued interim guidance for clinicians on identifying and caring for patients with novel H1N1, in addition to providing interim guidance on the use of antiviral drugs. Influenza antiviral drugs are prescription medicines (pills, liquid or an inhaler) with activity against influenza viruses, including novel influenza H1N1 viruses. The priority use for influenza antiviral drugs during this outbreak is to treat severe influenza illness, including people who are hospitalized or sick people who are considered at high risk of serious influenza-related complications.

Public Guidance

In addition, CDC has provided guidance for the public on what to do if they become sick with flu-like symptoms, including infection with novel H1N1. CDC also has issued instructions on taking care of a sick person at home. Novel H1N1 infection has been reported to cause a wide range of symptoms, including fever, cough, sore throat, body aches, headache, chills and fatigue. In addition, a significant number of people also have reported nausea, vomiting or diarrhea. Everyone should take everyday preventive actions to stop the spread of germs, including frequent hand washing and people who are sick should stay home and avoid contact with others in order to limit further spread of the disease.


CDC has developed a PCR diagnostic test kit to detect this novel H1N1 virus and has now distributed test kits to all states in the U.S. and the District of Columbia and Puerto Rico. The test kits are being shipped internationally as well. This will allow states and other countries to test for this new virus. This increase in testing will likely result in an increase in the number of confirmed cases of illness reported. This, combined with ongoing monitoring through Flu View should provide a fuller picture of the burden of disease in the United States over time.

See also the FluView Surveillance Report for the week ending May 9, 2009.

More on the Situation

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