Viruses 2010, 2(4), 782-795; doi:10.3390/v2040782
Article

Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee, WI

1,2,3,4,5,* email, 2,4,5email, 2,4,5email, 2,4,5email, 2,3,5email, 3,6email, 2email, 1,4email, 1,4email, 1,4email, 2email, 1,4email and 1,2,4,5email
Received: 7 December 2009; in revised form: 10 February 2010 / Accepted: 8 March 2010 / Published: 25 March 2010
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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 28th 2009–July 25th 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.
Keywords: influenza; pandemic; H1N1
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MDPI and ACS Style

Kumar, S.; Chusid, M.J.; Willoughby, R.E.; Havens, P.L.; Kehl, S.C.; Ledeboer, N.A.; Simpson, P.; VanDyke, M.; Davis, E.; Gaffney, K.; Li, S.-H.; Bose, M.E.; Henrickson, K.J. Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee, WI. Viruses 2010, 2, 782-795.

AMA Style

Kumar S, Chusid MJ, Willoughby RE, Havens PL, Kehl SC, Ledeboer NA, Simpson P, VanDyke M, Davis E, Gaffney K, Li S-H, Bose ME, Henrickson KJ. Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee, WI. Viruses. 2010; 2(4):782-795.

Chicago/Turabian Style

Kumar, Swati; Chusid, Michael J.; Willoughby, Rodney E.; Havens, Peter L.; Kehl, Sue C.; Ledeboer, Nathan A.; Simpson, Pippa; VanDyke, Meredith; Davis, Elizabeth; Gaffney, Kate; Li, Shun-Hwa; Bose, Michael E.; Henrickson, Kelly J. 2010. "Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee, WI." Viruses 2, no. 4: 782-795.


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