Epidemiology and Infection

Short Report

Zoonoses and animal infections

Estimated cumulative incidence of West Nile virus infection in US adults, 1999–2010

L. R. PETERSENa1 c1, P. J. CARSONa2a3, B. J. BIGGERSTAFFa1, B. CUSTERa4, S. M. BORCHARDTa2a5a6 and M. P. BUSCHa4a7

a1 Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins CO, USA

a2 University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA

a3 Sanford Health, Fargo, ND, USA

a4 Blood Systems Research Institute, San Francisco, CA, USA

a5 Fargo Veterans Affairs Medical Center, Fargo, ND, USA

a6 Wisconsin Department of Health, Madison, WI, USA

a7 University of California San Francisco, San Francisco, CA, USA


West Nile virus (WNV) was first recognized in the USA in 1999. We estimated the cumulative incidence of WNV infection in the USA from 1999 to 2010 using recently derived age- and sex-stratified ratios of infections to WNV neuroinvasive disease (WNND) and the number of WNND cases reported to national surveillance. We estimate that over 3 million persons have been infected with WNV in the USA, with the highest incidence rates in the central plains states. These 3 million infections would have resulted in about 780 000 illnesses. A substantial number of WNV infections and illnesses have occurred during the virus' first decade in the USA.

(Received February 29 2012)

(Revised April 15 2012)

(Accepted May 08 2012)

(Online publication May 28 2012)

Key words

  • Epidemiology;
  • incidence;
  • West Nile virus;
  • zoonoses


c1 Author for correspondence: L. R. Petersen, MD, MPH, Centers for Disease Control and Prevention, 3150 Rampart Road, Fort Collins, CO 80521, USA. (Email: lxp2@cdc.gov)