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. 2016 Jun;144(8):1792-802.
doi: 10.1017/S0950268815003131.

Evolving epidemiology of reported cryptosporidiosis cases in the United States, 1995-2012

J E Painter  1 , J W Gargano  2 , J S Yoder  2 , S A Collier  2 , M C Hlavsa  2
Affiliations

Evolving epidemiology of reported cryptosporidiosis cases in the United States, 1995-2012

J E Painter et al. Epidemiol Infect. 2016 Jun.

Abstract

Cryptosporidium is the leading aetiology of waterborne disease outbreaks in the United States. This report briefly describes the temporal and geographical distribution of US cryptosporidiosis cases and presents analyses of cryptosporidiosis case data reported in the United States for 1995-2012. The Cochran-Armitage test was used to assess changes in the proportions of cases by case status (confirmed vs. non-confirmed), sex, race, and ethnicity over the study period. Negative binomial regression models were used to estimate rate ratios (RR) and 95% confidence intervals (CI) for comparing rates across three time periods (1995-2004, 2005-2008, 2009-2012). The proportion of confirmed cases significantly decreased (P < 0·0001), and a crossover from male to female predominance in case-patients occurred (P < 0·0001). Overall, compared to 1995-2004, rates were higher in 2005-2008 (RR 2·92, 95% CI 2·08-4·09) and 2009-2012 (RR 2·66, 95% CI 1·90-3·73). However, rate changes from 2005-2008 to 2009-2012 varied by age group (P interaction < 0·0001): 0-14 years (RR 0·55, 95% CI 0·42-0·71), 15-44 years (RR 0·99, 95% CI 0·82-1·19), 45-64 years (RR 1·47, 95% CI 1·21-1·79) and ⩾65 years (RR 2·18, 95% CI 1·46-3·25). The evolving epidemiology of cryptosporidiosis necessitates further identification of risk factors in population subgroups. Adding systematic molecular typing of Cryptosporidium specimens to US national cryptosporidiosis surveillance would help further identify risk factors and markedly expand understanding of cryptosporidiosis epidemiology in the United States.

Keywords: Cryptosporidium; water-borne infections.

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Figures

Fig. 1.
Fig. 1.
Incidence rate of reported cryptosporidiosis, by case status and year, United States, 1995–2012 (N = 102 835).
Fig. 2.
Fig. 2.
Incidence rate of reported cryptosporidiosis/100 000 population, by county, United States, 1995–2012. (a) 1995–1999, (b) 2000–2004, (c) 2005–2008, (d) 2009–2012.
Fig. 3.
Fig. 3.
Percentage* of reported cryptosporidiosis cases, by sex and year, United States, 1995–2012. [* N = 101 823 cases: missing sex data for n = 1012 (1·0%) cases.]
Fig. 4.
Fig. 4.
Incidence rate of reported cryptosporidiosis, by county, by age group and year, United States, 1995–2012 (N = 102 835).
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