H1N1 Influenza in Boston: Past, Present, and Future Media Briefing Boston Public Health Commission August 17, 2009

Age Distribution of Cases As of July 31, 2009, 480 cases of confirmed novel H1N1 influenza have been identified in Boston. Of the confirmed cases, 296 (62%) are under 18 years of age, with a median age of % of cases are under age 5 and 91% are under age 45; only 41 cases (9%) have been over age 45.

Novel H1N1 Diagnosing Health Care Sites: April-July, 2009

Weekly incidence rates of H1N1 Influenza cases, by zipcode April 26 to June 6, 2009

Gender of Novel H1N1 Cases Compared to the Boston Population

Race/Ethnicity of Novel H1N1 Cases Compared to the Boston Population

Race/Ethnicity of Hospitalized Novel H1N1 Influenza Cases Black35 (49%) Hispanic20 (28%) Other5(7%) White11 (15%)

Characteristics of 71 Hospitalized Novel H1N1 Boston Cases CharacteristicN (%) Age Group0-4 years20 (28%) 5-17 years22 (31%) years16 (23%) years8 (11%) 65+ years5 (7%) ICU Admission26 (37%) Asthma35 (49%) Pneumonia26 (37%) Respiratory SupportCPAP/BIPAP10 (14%) Intubation7 (10%)

Reported Influenza A* and Novel H1N1 Influenza by Neighborhood: April-July, 2009 *Estimated that the majority were H1N1 Novel H1N1 = 477 cases; Influenza A = 508 cases

ED Visits for Influenza-like Illness (ILI) Summary of Boston Emergency Department Visits Time period (60 days)Total Visits* Visits for ILI** (% of all visits) April 15 - June 14, ,9153,907(4.1%) April 15 - June 14, ,122652(0.7%) January 7 - March 8, ,9041,688(1.9%) (2009 influenza season) *visits to 10 Boston emergency departments **ILI defined as "flu" or "fever and a respiratory symptom", as described in the patient's chief complaint The Boston Public Health Commission closely monitors emergency department visits for influenza-like illness (ILI) and other respiratory conditions. From April 15 to June 14, 2009, total visits and visits for ILI increased significantly. During that period 4.1% of all visits were for ILI, compared with 0.7% during the same time period in 2008, and 1.9% during the peak of the 2009 seasonal influenza season, from January 7 to March 8, 2009.

Percent of Emergency Department Visits for Influenza-like Illness 2009 vs. prior years

Estimated impact of H1N1 by neighborhood Estimated Cases Populatio n*% Affected Boston, MA23,388589,2304.0% Overall neighborhood estimates, by percent affected Above Citywide average (>4.3%)Est. CasesPopulation% Affected East Boston3,08238,4138.0% Roxbury2,07734,6656.0% Fenway2,69847,4495.7% Allston/Brighton3,29666,4675.0% North Dorchester3,01858,6755.1% South Dorchester3,44475,3294.6% Mattapan1,22627,8154.4% Total, neighborhoods with high activity18,841348,8135.4% Below Citywide average (<4.3%) Hyde Park1,02928,3923.6% Roslindale1,16832,5273.6% Charlestown42015,1952.8% South Boston54230,0481.8% South End39727,3111.5% Jamaica Plain32936,2930.9% Back Bay/Beacon Hill/West End/North End/Downtown23246,2580.5% West Roxbury16924,0580.7% Total, neighborhoods with low activity4,286240,0821.8%

School Closings High, sustained rates of absenteeism caused by influenza-like illness led to temporary school closures in certain instances. School closures were recommended on a case by case basis, and lasted an average of 7 days.

Burden of H1N1 Influenza Activity: School Assessment Findings Compared to schools that remained open, closed schools: – experienced greater burden of H1N1 influenza activity, as measured by staff out sick and students sent home sick – were more likely to report difficulty keeping ill students out of school (44% vs. 27%)

Percent Attendance in Closed Boston Public Schools SchoolFebruary BaselinePre-Closure*Post-Closure* A B C9488 D E F G H I J K928486