June 10, 2009 – The Health Department today released preliminary findings from a household survey designed to estimate the prevalence of flu-like illness in New York City during the first three weeks of May. Some 6.9% of the New Yorkers surveyed said they had experienced flu-like illness between May 1 and May 20. Flu-like illness was defined as having a fever accompanied by either cough or sore throat – symptoms that can reflect a range of different illnesses. “The findings don’t tell us exactly how many New Yorkers have had H1N1 influenza,” said Dr. Thomas Farley, New York City Health Commissioner. “But they suggest it has been widespread, and mild in most affected people.”
Illness and emergency room visits for flu-like illness have recently declined city-wide. As anticipated, however, some of the illness has resulted in hospitalizations and deaths. Since late April, 530 New Yorkers have been hospitalized with H1N1 flu, and 12 deaths have been linked to the virus.
The city-wide survey, conducted by telephone from May 21 through May 27, found that overall prevalence of reported flu-like illness was highest in Queens, where 9.4% of respondents reported symptoms, and Brooklyn (8.9%), followed by Staten Island (4.2%), Manhattan (3.7%) and the Bronx (3.6%). Queens also reported the most influenza-like illness among children, with 16% of those affected being under the age of 18.
Because the outbreak of H1N1 in New York City did not begin to spread widely until mid-May, some people who reported flu-like illness in the survey may have had seasonal flu, strep throat, or other illnesses that resembled flu. It is not yet clear what proportion of those with flu-like illness had the H1N1 virus, but all evidence suggests it has spread widely within New York City. Other indicators suggest the peak period of H1N1 activity in this outbreak may have occurred after the survey was completed.
The survey also found the prevalence of influenza-like illness was twice as high among children as among adults between 18 and 64, and was lowest among those 65 and older. “This survey suggests that many thousands – perhaps hundreds of thousands – of New Yorkers may have had flu-like illness due to the H1N1 virus, and a very small proportion of them developed severe disease,” said Dr. Thomas Farley, New York City Health Commissioner.
Additional H1N1-related deaths identified
The Health Department today linked three more deaths to H1N1 influenza. The latest fatalities involved one person aged 30-39, one aged 50-59, and one who was over 65. To safeguard patient privacy, the Health Department does not report on the clinical details of individual cases. While most of New York City’s H1N1 flu deaths have occurred in people with established risk factors for flu complications, influenza is sometimes fatal in otherwise-healthy people. New Yorkers who are less than 2 or 65 or over, women who are pregnant or others with underlying health conditions should call a doctor right away if they develop flu-like illness, and anyone who develops severe flu symptoms, such as difficulty breathing, should seek immediate medical attention. See the link below for more information on risk factors for flu complications: http://www.nyc.gov/html/doh/downloads/pdf/cd/h1n1_flu_what_to_do_flyer.pdf.
About the Survey
From May 20 to May 27, 2009, the Health Department commissioned a random telephone survey of 1,006 New York City households. Approximately 700 households were surveyed between May 20 and May 22, and the remainder was surveyed on May 26 and May 27, after the Memorial Day Weekend. The survey questionnaire asked respondents whether they had experienced fever accompanied by cough or sore throat during April or May. For those who answered yes, additional questions were asked about maximum temperature, days lost from work, visits to the doctor, diagnoses and prescription of medication to treat flu. The survey questionnaire also enumerated all individuals within each household by age group (0 to 17, 18 to 64, 65 and older) and recorded the number of individuals who had experienced ILI during May.