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Cryptosporidiosis is a gastrointestinal illness caused by protozoa of the genus Cryptosporidium, the leading cause of U.S. waterborne disease outbreaks (1) and the third leading cause of U.S. zoonotic enteric illness (2,3). An estimated 823,000 cryptosporidiosis cases occur annually; this means <2% of cases are nationally notified. Cryptosporidium infection can be symptomatic or asymptomatic. Immunocompetent patients can experience frequent, non-bloody, watery diarrhea typically lasting up to three weeks (4). Additional symptoms can include vomiting, nausea, abdominal pain, fever, anorexia, fatigue, and weight loss. Immunocompromised patients can experience profuse watery diarrhea lasting weeks to months or even life-threatening malnutrition and wasting (5).

Cryptosporidiosis is a nationally notifiable disease; the first full year of reporting was 1995. National data are collected through passive surveillance. Healthcare providers and laboratories that diagnose cryptosporidiosis are mandated to report cases to the local, state, or territorial health department. The 50 states, District of Columbia (DC), New York City (NYC), and territorial public health agencies, in turn, voluntarily notify obÌåÓý of cases via the National Notifiable Disease Surveillance System (NNDSS). Although tribes do not report directly to obÌåÓý via NNDSS, the inclusion of case data submitted by states for American Indian and Alaskan Native individuals residing on tribal lands may vary based on laboratory and case reporting practices in each jurisdiction, the location where healthcare services were delivered, and other relevant factors. Some jurisdictions conduct enhanced molecular surveillance of cryptosporidiosis through participation in CryptoNet; CryptoNet data are not presented here.

State, territorial, local, and tribal health agencies voluntarily notify obÌåÓý of cryptosporidiosis outbreaks via the National Outbreak Reporting System (NORS). NORS data are not presented here; however, summaries of data on waterborne disease outbreaks are reported elsewhere.

The of a confirmed case of cryptosporidiosis has changed over time. The was published in 1995 (6); the was published in 2012 (7). The pre-2011 case definitions classified a case with any laboratory evidence of Cryptosporidium infection as a confirmed case.

The 2012 confirmed case definition requires evidence of Cryptosporidium organisms or DNA in stool, intestinal fluid, tissue samples, biopsy specimens, or other biological sample by certain laboratory methods with a high positive predictive value (e.g., direct fluorescent antibody [DFA] test, polymerase chain reaction [PCR], enzyme immunoassay [EIA], or light microscopy of stained specimen).

A probable case of cryptosporidiosis is defined as 1) having supportive laboratory test results for Cryptosporidium spp. infection using a screening test method, such as immunochromatographic card or rapid card test, or a laboratory test of unknown method or 2) meeting clinical criteria (diarrhea and one or more of the following: diarrhea duration of >72 hours, abdominal cramping, vomiting, or anorexia) and being epidemiologically linked to a confirmed case.

A suspect case is defined as having a diarrheal illness and being epidemiologically linked to a probable case. Cases not classified as confirmed, probable, or suspect are classified as unknown.

National cryptosporidiosis surveillance data for 2022 were analyzed using R version 4.4.1. Data cleaning processes included case deduplication and the verification of case status (confirmed or nonconfirmed). Numbers, percentages, and incidence rates (cases per 100,000 population) of cryptosporidiosis were calculated in aggregate for the United States and separately for each reporting jurisdiction. Rates were calculated by dividing the number of cryptosporidiosis cases by each year's mid-year census estimates (8,9) and multiplying by 100,000.

U.S. Census Bureau data were obtained using its Application Programming Interface and the R "tidycensus" package (10,11). Region and total population estimates included only jurisdictions that reported (Figure 2). In addition to analyzing data nationally and by reporting jurisdiction, data were analyzed by region (Northeast, Midwest, South, West, and Territories), as defined by the U.S. Census Bureau (12). To account for differences in the seasonal use of recreational water, the West region was further subdivided into Northwest and Southwest.

To examine reporting over time, cryptosporidiosis rates were calculated by year (2013 to 2022). To examine changes in cryptosporidiosis reporting in 2022 attributed to the COVID-19 pandemic, we calculated the percent change in incidence between 2021 and 2022. We also calculated the five-year average-annual incidence (2018–2022). Annual cryptosporidiosis rates were calculated by demographic variables (age and sex) and jurisdiction. Rates were not calculated for race or ethnicity due to large proportion of missing data for these variables (12.1% and 22.9% respectively).

In 2022, 54 jurisdictions reported cryptosporidiosis case data to NNDSS, including 50 states, 2 territories, DC, and New York City. There were 12,609 cases of cryptosporidiosis reported to obÌåÓý with an average annual incidence of 3.8 cases per 100,000 population (Figure 1, Table 1). Reported cases of cryptosporidiosis in 2022 were higher than those reported in 2021, with a 40.7% increase in incidence from 2021 (incidence rate of 2.7 cases per 100,000) (Table 1). This higher rate is attributed, in part, to the COVID-19 pandemic during 2020 and 2021, when health care providers and local and state health departments in the United States may have had lower capacity to detect, investigate, and report cases. An increase in incidence was observed across a majority (75.9%) of reporting jurisdictions (n=41/54) (Table 1), with the percent increase in incidence ranging from 2.3% to 261.1%. Twelve jurisdictions had an observed decrease or no change in incidence between 2021 and 2022. Of the 12,609 reported cases in 2022, 10,171 (80.7%) were confirmed, while 2,438 cases (19.3%) were not confirmed. This is a slight increase in the proportion of confirmed cases compared with 2021 (78.4%), with the proportion of confirmed cryptosporidiosis cases increasing over time, with 62.8% confirmed in 2013. There were 165 outbreak-associated cases reported in 2022.

Cryptosporidiosis is geographically widespread across the United States. By region, incidence of reported cryptosporidiosis cases ranged from 2.7 cases per 100,000 population in the Southwest to 5.6 cases per 100,000 population in the Midwest. In 2022, territorial jurisdictions had an incidence of 0.1 cases per 100,000 population, with the Northern Mariana Islands and Puerto Rico reporting cases in 2022. By jurisdiction, cryptosporidiosis incidence ranged from 0.0 per 100,000 population in Puerto Rico and 0.4 per 100,000 in DC to 14.9 per 100,000 population in Iowa (Table 1, Figure 2). Differences in incidence might reflect differences in risk factors or mode of transmission of cryptosporidium; the magnitude of outbreaks; or the capacity or requirements to detect, investigate, and report cases.

For cases with a reported symptom onset date, most cases occurred between July and September, with a peak in August (n=1,228) (Figure 3). When separated by region, the Northeast, Midwest, and South had the most well-defined peak in cases during July through September (Figure 4).

During 2022, a total of 5,740 cases were male (45.5%) and 6,816 (54.1%) were female (Table 2). Most cases for which data on race were available occurred among the classifications White (70.9%), Black (8.1%), other or Multi-race (6.2%), and Asian/Pacific Islander (2.2%). Most patients for whom data on ethnicity were available were non-Hispanic (66.1%). Data on race were not reported for 12.1% of cases, and data on ethnicity were not reported for 22.9% of cases.

With respect to age, the incidence of reported cryptosporidiosis cases was highest in persons aged <5 years (incidence rates = 5.8 cases per 100,000 population), with secondary peaks between 25–34 years and 80–84 years (incidence rates >4.5 per 100,000 population) (Figure 5). With respect to sex, the highest incidence of cryptosporidiosis was among boys ages <5 years (6.6 cases per 100,000 population). For most age groups, however, female patients had a higher rate than male patients (Figure 6).

This report is based on contributions by state and local epidemiologists and microbiologists. The authors gratefully acknowledge Zainab Salah for assistance in reviewing code, and thank Samaria Aluko-Estrella, Amanda MacGurn, Vince Hill, and Jeremy Sobel for their assistance in publishing this annual report.

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^* Cases per 100,000 population

^§ In total, 76,401 cases were confirmed (70.6%); 31,881 cases were non-confirmed (29.4%). For 2022, 10,171 cases were confirmed (80.7%); 2,438 cases were non-confirmed (19.3%).

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Abbreviation NR = Non-Reporting Jurisdiction

^*Percentages might not total 100% because of rounding

^§ Cases per 100,000 population

^¶New York State and New York City data are mutually exclusive

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^*Cases per 100,000 population

^§ Non-continental jurisdictions (i.e., Alaska, Hawaii, and U.S. territories) are not shown to scale and are not meant to depict their true geographic location.

^¶New York State and New York City data are mutually exclusive

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^*Percentages might not total 100% because of rounding

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^*Date of onset was available for 72.8% of reported cases (n=9,177/12,609)

Midwest

Northeast

South

Southwest

Territory^§

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^*Date of onset was available for 72.8% of reported cases (n=9,177/12,609)

^§Territorial jurisdictions had two cases: one with illness onset in May and the other with illness onset in August.

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^*Cases per 100,000 population

^§ Age data are available for 99.9% of reported cases (n=12,595/12,609)

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^*Cases per 100,000 population

^§ Age and sex data are available for 99.5% of reported cases (n=12,542/12,609)