Epidemiology and Infection

  • Epidemiology and Infection / Volume 142 / Issue 01 / January 2014, pp 163-171
  • Copyright © Cambridge University Press and World Health Organization 2013 WHO has granted permission to Cambridge University Press to publish the contribution written by WHO. This article may not be reprinted or reused in any way in order to promote any commercial products or services. Parts of this are a work of the U.S. Government and not subject to copyright protection in the United States.
  • DOI: http://dx.doi.org/10.1017/S0950268813000800 (About DOI), Published online: 18 April 2013

Original Papers


Surveillance during an era of rapidly changing poliovirus epidemiology in India: the role of one vs. two stool specimens in poliovirus detection, 2000–2010


a1 Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA

a2 Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA, USA

a3 World Health Organization – India, National Polio Surveillance Project, New Delhi, India

a4 Ministry of Health and Family Welfare, Government of India, New Delhi, India

a5 Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA


Since 2004, efforts to improve poliovirus detection have significantly increased the volume of specimen testing from acute flaccid paralysis (AFP) patients in India. One option to decrease collection and testing burden would be collecting only a single stool specimen instead of two. We investigated stool specimen sensitivity for poliovirus detection in India to estimate the contribution of the second specimen. We reviewed poliovirus isolation data for 303984 children aged <15 years with AFP during 2000–2010. Using maximum-likelihood estimation, we determined specimen sensitivity of each stool specimen, combined sensitivity of both specimens, and sensitivity added by the second specimen. Of 5184 AFP patients with poliovirus isolates, 382 (7·4%) were identified only by the second specimen. Sensitivity was 91·4% for the first specimen and 84·5% for the second specimen; the second specimen added 7·3% sensitivity, giving a combined sensitivity of 98·7%. Combined sensitivity declined, and added sensitivity increased, as the time from paralysis onset to stool collection increased (P = 0·032). The sensitivity added by the second specimen is important to detect the last chains of poliovirus transmission and to achieve certification of polio eradication. For sensitive surveillance, two stool specimens should continue to be collected from each AFP patient in India.

(Received November 19 2012)

(Revised March 08 2013)

(Accepted March 08 2013)

(Online publication April 18 2013)

Key words

  • Infectious disease epidemiology;
  • laboratory tests;
  • polio;
  • surveillance;
  • surveillance system


c1 Author for correspondence: Dr C. V. Cardemil, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333, USA. (Email: ccardemil@cdc.gov)