Template:2009 US swine flu outbreak table/doc

Case Classification
The CDC has defined three classifications for investigations of Swine-Origin Influenza A H1N1 Cases (S-OIV).


 * Confirmed: a person with an acute febrile respiratory illness with laboratory confirmed S-OIV infection by one or more of the following tests:
 * real-time RT-PCR
 * viral culture


 * Probable: a person with an acute febrile respiratory illness who is positive for influenza A, but negative for H1 and H3 by influenza RT-PCR


 * Suspected: a person with acute febrile respiratory illness with onset
 * within 7 days of close contact with a person who is a confirmed case of S-OIV infection, or
 * within 7 days of travel to community either within the United States or internationally where there are one or more confirmed cases of S-OIV infection, or
 * resides in a community where there are one or more confirmed cases of S-OIV infection.

Daily Reporting
The CDC releases a daily update on confirmed cases by state at 11:00 am ET. Many state departments of health release updates on confirmed and probable cases throughout the day. Several states have developed dedicated websites for information on the flu outbreak. Others release numbers on their department of health website or though daily press reports.

All U.S. States and Puerto Rico have received testing kits and training from the CDC that permits them to do local confirmation of samples. Previously all samples had to be sent to CDC headquarters in Atlanta, causing considerable delay in reporting.

The numbers from state authorities are often out of synch with those in the CDC daily report, primarily because the CDC updates its figures less frequently. For instance, the Illinois Department of Public Health updated the number of confirmed cases in Illinois to 225 at 10 a.m. CT on May 6, 2009, while the CDC update at 11:00 AM ET that day showed only 122 confirmed cases in Illinois. The CDC report also currently lists one trans-state case. A Kentucky woman who had returned home from Mexico later traveled to Georgia where she was diagnosed and treated for swine flu. Both Georgia and Kentucky record the case on their websites; the CDC notes the case for Kentucky.

Some states, including Michigan, Massachusetts, Tennessee, have stopped reporting probable numbers since receiving their CDC testing kits.

On May 14 the CDC changed its daily report from only confirmed cases to 'Confirmed and Probable cases'.

In early June the CDC changed from daily reporting to weekly reporting. The CDC report is published each Friday at 11:00 based on numbers reported by 3pm the previous day.

Changes of Fundamental Reporting Principles
Several states have abandoned the counting of confirmed cases. In the second half of June Michigan has moved to 'aggregate flu reporting', where no difference is made between novel (pandemic) flu and seasonal flu. This step is justified by the finding, that at this point of the year more than 98% of detected flu cases are caused by the novel flu. Other states, such as Utah (early June) and Washington (end of May), have started to report the number of hospitalized cases instead of infected cases. This new approach surely excludes many sources of error, but it hampers comparisons between states and over time.

The CDC discontinued reporting of individual confirmed and probable cases of novel H1N1 infection on July 24, 2009. The CDC will report the total number of hospitalizations and deaths weekly, and continue to use its traditional surveillance systems to track the progress of the novel H1N1 flu outbreak.