title: Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee, WI.
abstract: The first wave of the 2009 influenza H1N1 pandemic (H1N1pdm) in Milwaukee, WI has been recognized as the largest reported regional outbreak in the United States. The epidemiologic and clinical characteristics of this large first wave outbreak from April 28(th) 2009-July 25(th) 2009, studied using both passive and targeted surveillance methodologies are presented. A total of 2791 individuals with H1N1pdm infection were identified; 60 % were 5-18 years old. The 5-18 year and 0-4 year age groups had high infection (1131 and 1101 per 100,000) and hospitalization (49 and 12 per 100,000) rates respectively. Non-Hispanic blacks and Hispanics had the highest hospitalization and infection rates. In targeted surveillance, infected patients had fever (78%), cough (80%), sore throat (38%), and vomiting or diarrhea (8%). The "influenza like illness" definition captured only 68 % of infected patients. Modeling estimates that 10.3 % of Milwaukee population was infected in the first wave and 59% were asymptomatic. The distinct epidemiologic profile of H1N1pdm infections observed in the study has direct implications for predicting the burden of infection and hospitalization in the next waves of H1N1pdm. Careful consideration of demographic predictors of infection and hospitalization with H1N1pdm will be important for effective preparedness for subsequent influenza seasons.
authors.affiliation: Midwest Respiratory Virus Program (MRVP), Suite C450, Pediatric Infectious Diseases, Children's Hospital of Wisconsin, P.O. Box 1997, Milwaukee, WI 53201-1997,USA; mvandyke@mcw.edu (M.V.); edavis@mcw.edu (E.D.); kgaffney@mcw.edu (K.G.); mbose@mcw.edu (M.E.B.); khenrick@mcw.edu (K.J.H.).
authors.forename: Swati
authors.initials: S
authors.lastname: Kumar
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Chusid
authors.forename: Rodney E
authors.initials: RE
authors.lastname: Willoughby
authors.forename: Peter L
authors.initials: PL
authors.lastname: Havens
authors.forename: Sue C
authors.initials: SC
authors.lastname: Kehl
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ledeboer
authors.forename: Pippa
authors.initials: P
authors.lastname: Simpson
authors.forename: Meredith
authors.initials: M
authors.lastname: Vandyke
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Davis
authors.forename: Kate
authors.initials: K
authors.lastname: Gaffney
authors.forename: Shun-Hwa
authors.initials: SH
authors.lastname: Li
authors.forename: Michael E
authors.initials: ME
authors.lastname: Bose
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Henrickson