June 12, 2009 — Community transmission of the H1N1 virus appears to be declining in New York City, as emergency departments report lower numbers of visits due to influenza-like illness, the Health Department reported today. As expected, however, hospitalizations and fatalities continue to occur. As of June 11, the Health Department had recorded 567 hospitalizations and 16 deaths. The latest death occurred in a person aged 40-49. 

As the charts on the next page illustrate, emergency-department visits for flu-like illness surged during May, reaching a peak on May 25, but have since declined markedly. Hospital admissions for H1N1 influenza have also declined — after peaking on May 27. "The Health Department monitors influenza-like illness every day in New York City," said Dr. Thomas Farley, New York City Health Commissioner. "While every hospitalization is concerning and every death is a tragedy, our surveillance data indicate that the number of people newly infected is declining."

Of the 16 New York City deaths attributed to H1N1 flu, 14 have occurred in people under 65, and 12 of the decedents (75%) have had an established underlying risk factor (PDF) for developing severe influenza or complications. All four of the others have been obese, a condition that is not a known risk factor for severe illness but which could potentially increase the risk of complications from flu. Further study is needed to evaluate this finding.

The hospitalized patients have been younger than those who normally experience severe illness during a seasonal flu outbreak. Some 79% of the hospitalized patients have been younger than 50. Nearly half (46%) have been younger than 18, and 20% have been under 5. Only 5% of New Yorkers hospitalized with H1N1 have been 65 or older. Residents from all five boroughs have been hospitalized, with the majority of hospitalizations occurring in residents of Brooklyn (32%) and the Bronx (29%), followed by Queens (23%), Manhattan (14%) and Staten Island (2%).

Of the 567 hospitalizations, 80% of the patients had at least one known risk factor for severe illness or complications due to influenza. The most common risk factor is asthma, which has been found in 41% of all confirmed hospitalized cases. Other important risk factors include pregnancy (noted in 28% of the 142 women of childbearing age hospitalized for confirmed H1N1), age less than 2 years (12%), diabetes (11%), weakened immunity (9%), and cardiovascular disease (9%). 

While most of the influenza now circulating in New York City is H1N1, seasonal flu is still present at low levels. The Health Department's Public Health Laboratory identified seasonal flu in 10% of all flu samples tested during this outbreak.

> View a larger table.

Figure 1 — An emergency department (ED) visit for influenza-like illness (ILI) is defined as a visit in which a person's complaint includes fever with either cough or sore throat or the mention of the word "flu." ED ILI data are collected from 50 hospitals representing 95% of annual ED visits in NYC. Visits to emergency departments can be affected by several factors, including how worried people are about flu, whether people can see their own doctor, media announcements, etc. The data are most useful for following trends over several days. Laboratory-confirmed H1N1 hospital admissions likely under represent total hospitalizations as H1N1 screening tests for influenza do not accurately identify the presence of the virus in all cases. Note that data on H1N1 hospitalizations lag behind ED visits due to the reporting and laboratory testing intervals.

> View a larger table.

Figure 2 — Graph presents rates of influenza-like illness (ILI) visits to 50 New York City emergency departments by four age categories. The data does not represent confirmed H1N1 cases. The figure shows that children less than 4 years old (yellow line) have a higher background rate of ILI and that the age group most affected during the current outbreak is 5 to 17-year-olds (red line). The rate of ILI visits for individuals 65 years and older (blue line) does not appear to have changed from the background rate.

Earlier this week, the Health Department released preliminary findings from a household survey suggesting that 6.9% of New Yorkers may have experienced flu-like illness between May 1 and May 20. 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. While not all those with flu-like illness had H1N1 influenza, these results suggest that H1N1 infections were common at that time, especially in Queens and Brooklyn.

Symptoms of H1N1 (SO) include fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting as well. Any New Yorker experiencing severe symptoms, such as difficulty breathing, should seek immediate health care and treatment. New Yorkers with an underlying health condition should immediately call their doctor if they experience flu-like illness, or come into contact with someone who has the flu.

Actions that anyone can take to slow the spread of influenza:

• Cover your mouth when you cough with your sleeve or a tissue or handkerchief.
• Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hand cleaners are also effective.
• Try to avoid close contact with sick people.
• If you are sick with fever and either a cough or sore throat, stay home for at least 24 hours after all of your symptoms are gone.
• Stay away from clinics and hospitals unless you have severe symptoms, and notify your doctor or the clinic before, or as soon as you arrive, that you have a fever and respiratory systems so that you can be appropriately isolated from others.

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