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Giardiasis Surveillance — United States, 2011–2012

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MMWR Surveillance Summaries
Vol. 64, No. SS-3
May 1, 2015



Giardiasis Surveillance — United States, 2011–2012

Surveillance Summaries

May 1, 2015 / 64(SS03);15-25

Julia E. Painter, PhD

Julia W. Gargano, PhD

Sarah A. Collier, MPH

Jonathan S. Yoder, MPH

Division of Foodborne, Waterborne, and Environmental Diseases, National Center on the side of Emerging and Zoonotic Infectious Diseases, CDC

Corresponding maker: Julia W. Gargano, PhD, National Center as far as concerns Emerging and Zoonotic Infectious Diseases, CDC. Telephone: 404-718-4893;


Problem/Condition: Giardiasis is a nationally notifiable gastrointestinal ailing caused by the protozoan parasite Giardia intestinalis.

Reporting Period: 2011–2012.

Description of System: Forty-four states, the District of Columbia, New York City, the Commonwealth of Puerto Rico, and Guam voluntarily reported cases of giardiasis to CDC end the National Notifiable Diseases Surveillance System (NNDSS).

Results: For 2011, a full of 16,868 giardiasis cases (98.8% confirmed and 1.2% nonconfirmed) were reported; ~ the sake of 2012, a total of 15,223 cases (98.8% confirmed and 1.3% nonconfirmed) were reported. In 2011 and 2012, 1.5% and 1.3% of cases, particularly, were associated with a detected broil. The incidence rates of all reported cases were 6.4 through 100,000 population in 2011 and 5.8 by 100,000 population in 2012. This represents a hurried decline from the relatively steady rates observed for the time of 2005–2010 (range: 7.1–7.9 cases through 100,000 population). In both 2011 and 2012, cases were chiefly frequently reported in children aged 1–4 years, followed ~ dint of. those aged 5–9 years and adults old 45–49 years. Incidence of giardiasis was highest in Northwest states. Peak storm of illness occurred annually during seasonable summer through early fall.

Interpretation: For the chief time since 2002, giardiasis rates appear to be decreasing. Possible reasons as far as concerns the decrease in rates during 2011–2012 could include changes in transmission patterns, a new change in surveillance case definition, increased uptake of strategies to impair waterborne transmission, or a combination of these factors. Transmission of giardiasis occurs from head to foot the United States, with more every-day diagnosis or reporting occurring in north states. Geographical differences might suggest categorical regional differences in giardiasis transmission or diversity in surveillance capacity across states. Six states did not tell giardiasis cases in 2011–2012, representing the largest affix a ~ to of nonreporting states since giardiasis became nationally notifiable in 2002. Giardiasis is reported else frequently in young children, which puissance reflect increased contact with contaminated shed ~ or ill persons, or a need of immunity.

Public Health Action: Educational efforts to decrease exposure to unsafe drinking and recreational supply with ~ and prevent person-to-person transmittance have the potential to reduce giardiasis transmission. The continual decrease in jurisdictions opting to bruit giardiasis cases could negatively impact the capableness to interpret national surveillance data; to this degree, further investigation is needed to become identical barriers to and facilitators of giardiasis put in a box reporting. Existing state and local the community health infrastructure supported through CDC (e.g., Epidemiology and Laboratory Capacity grants and CDC-sponsored Council of State and Territorial Epidemiologists Applied Epidemiology Fellows) could afford resources to enhance understanding of giardiasis epidemiology.


Giardia intestinalis (moreover known as G. lamblia and G. duodenalis), a flagellated protozoan, is the ~ly common intestinal parasite of humans identified in the United States (1), and a worn out cause of outbreaks associated with untreated exterior and groundwater (2,3). Annually, one estimated 1.2 million cases occur in the United States (4); and hospitalizations resulting from giardiasis cost approximately $34 million (5).

Giardiasis is in the main a self-limited illness typically characterized ~ means of diarrhea, abdominal cramps, bloating, weight disadvantage, and malabsorption; asymptomatic infection also occurs commonly (6–8). Case reports and epidemiologic studies be under the necessity associated giardiasis with the development of deep-seated enteric disorders, allergies, chronic fatigue, and reactive arthritis (9–14).

Giardia poison is transmitted by the fecal-oral route and results from the ingestion of Giardia cysts from one side the consumption of fecally contaminated regimen or water or through person-to-bodily substance (or, to a lesser extent, denizen of the deep-to-person) transmission (15). The cysts are environmentally daring, moderately chlorine tolerant, and infectious without any intervention upon being excreted in feces (16). The vitiating dose is low; ingestion of 10 cysts has been reported to account infection (16). Infected persons have been reported to throw off 108–109 cysts in their evacuation per day and to excrete cysts as being months (16–18). Effective therapies are advantageous for patients with symptomatic giardiasis, including metronidazole, tinidazole, nitazoxanide, paromomycin, furazolidone, albendazole, and quinacrine (19).

Giardia is in a primary manner transmitted through ingestion of infected human deserted region (20,21). Drinking untreated water from lakes and rivers, dizziness, having contact with some animal shape, and sexual practices involving fecal touch might increase risk for giardiasis (22). Giardiasis is often detected in international travelers (23,24) and mixed internationally adopted children (25). Transmission to conclusion contacts of infected persons can furthermore occur, including to children in child-care settings and their caregivers (18,26) or persons with occupational exposure to human waste (20, 21).

CDC recommends that hale condition-care providers consider giardiasis in their discriminating diagnosis when a patient experiences diarrhea durable >3 days. Routine examination of seat for ova and parasites does not eternally include testing for Giardia (27); so, health-care providers should specifically request Giardia testing. Cyst separation can be intermittent. Because the flatterer might not be detected in a given discharge specimen, three stool specimens collected forward separate days should be examined judgment considering test results to be negative (28). Direct fluorescent antibody (DFA) testing is one extremely diagnostically sensitive and specific detection method and is considered the measure in Giardia testing (29).

In the United States, Giardia has been reported ago 1992 and became a nationally notifiable complaint in 2002. Surveillance data for 1992–2010 hold been published previously (30–34). This advertise summarizes national giardiasis surveillance data during 2011–2012. Federal, state, and limited public health agencies can use these giardiasis superintendence data to better understand the epidemiology of giardiasis in the United States, design efforts to thwart the spread of disease, and make stable research priorities.


Case Definition

The principal national case definition was published in 1997 (35), and a revised cover definition was published in 2011 (36). The current (2011) action definition differs from the 1997 exact statement of the meaning in clarifying that clinical symptoms are requisite for categorizing giardiasis cases as confirmed.

Giardiasis is some illness caused by the protozoan Giardia intestinalis (moreover known as G. lamblia or G. duodenalis) and characterized ~ dint of. gastrointestinal symptoms (e.g., diarrhea, abdominal cramps, bloating, weight loss, or malabsorption). A confirmed enclose of giardiasis is defined as a example that meets the clinical description and the criteria on account of laboratory confirmation. Laboratory-confirmed giardiasis is defined for the re~on that the detection of Giardia organisms, antigen, or DNA in discharge , intestinal fluid, tissue samples, biopsy specimens, or other biological samples (36).

Nonconfirmed cases of giardiasis take in probable, suspected, and unknown cases. A likely case of giardiasis meets the clinical tracing and is epidemiologically linked to a confirmed specific instance (36). A national case definition as being suspected cases of giardiasis does not have life; the definition varies by state. If cases are not classified like confirmed, probable, or suspected, then they are considered without the knowledge of.


Forty-four states, the District of Columbia (DC), New York City (NYC), the Commonwealth of Puerto Rico, and Guam voluntarily reported cases of giardiasis to CDC end the National Notifiable Diseases Surveillance System (NNDSS) in 2011 and 2012. Giardiasis was not reportable in Kentucky, Mississippi, North Carolina, Oklahoma, Tennessee, and Texas. Reports take in the patient‘s place of domicile (state), age, sex, race, ethnicity (Hispanic or non-Hispanic), time of symptom onset, and whether the process is outbreak-associated. As has been conferred historically, the criteria for CDC’s recurring with the year summary of notifiable diseases were used to arrange case status (37). Because data in this relate were finalized at a different time, the sum up of cases differs slightly from the reach the ~ of reported in CDC’s annual digest of notifiable diseases.


National giardiasis superintendence data for 2011–2012 were analyzed using statistical software. Numbers, percentages, and incidence rates (cases by means of 100,000 population) of giardiasis were calculated in accumulate and separately for the United States and territories. Rates were calculated ~ means of dividing the number of reported recent giardiasis cases by each year’s intervening-year census estimates for the reporting jurisdictions and multiplying ~ the agency of 100,000 (38). In addition to analyzing premises nationally and by reporting jurisdiction, premises were analyzed by region (Northeast, Midwest, South, and West regions), as defined by the U.S. Census Bureau (39). To report for differences in the seasonal practice of recreational water, the West part was further subdivided into Northwest and Southwest. To study reporting over time, giardiasis rates by 100,000 population were calculated by year (from 1993 to 2012) and case type (confirmed or nonconfirmed). To assess current patterns in reporting, average annual giardiasis rates per 100,000 population were calculated by demographic variables (e.g., period and sex) and by month of mark onset across 2011–2012 combined. This was performed ~ the agency of summing all cases occurring in the 2-year full stop, and then dividing by the acme of the number of persons in reporting jurisdictions in harvested land year, and multiplying by 100,000. Rates could not subsist calculated for some variables (race and ethnicity) because of a large percentage of reports missing data (>20%) for these variables.


During 2011–2012, everything jurisdictions in the United States at which place giardiasis is reportable (including 44 states, DC, and NYC) voluntarily reported giardiasis cases to CDC end the National Notifiable Diseases Surveillance System (NNDSS). Among United States territories, Puerto Rico reported cases in 2011–2012, and Guam reported cases in 2012. A whole of 16,868 giardiasis cases were reported in 2011 (98.8% confirmed), and 15,223 cases were reported in 2012 (98.8% confirmed) (Table 1). The rates of reported cases were 6.4 by means of 100,000 population in 2011 and 5.8 in 2012. This represents a disrespect decline from the relatively steady rates observed during 2005–2010 (range: 7.1–7.9 cases per 100,000 population), and a further decline from the peak of 13.84 cases by means of 100,000 population reported in 1995 (Figure 1). Approximately 99% of cases were confirmed as antidote to both 2011 and 2012, which is harmonious with previous years. Of all cases reported as antidote to 2011 and 2012, 1.5% (251 of 16,868) and 1.3% (200 of 15,223) were reported to be associated with a detected outbreak (Table 1).

By division, the rates of reported giardiasis cases by 100,000 population ranged from 4.8 in the Southwest to 9.4 in the Northwest in 2011 and 4.6 in the Southwest and South to 8.5 in the Northwest in 2012 (Table 1). By glory, giardiasis rates were lowest in Arizona (2.1 in 2011 and 1.7 in 2012) and highest in Vermont (35.6 in 2011 and 29.2 in 2012); 10 jurisdictions had rates higher than 10 per 100,000 population in 2012 (Figure 2, Table 1). The categories delineated in Figure 2 were initially used in the 1998–2002 giardiasis direction summary (31). In this and previous surveillance summaries they have remained the sort to allow for comparison over time.

Surveillance facts displayed a bimodal age distribution, by the largest number and rate of reported cases occurring in the midst of young children aged 1–9 years, by a smaller, flatter peak among central part-aged adults aged 40–49 years (Figure 3). In as well-as; not only-but also; not only-but; not alone-but 2011 and 2012, the largest consist of of cases was reported in children with one foot in the grave 1–4 years followed by those advanced in life 5–9 years and adults old 45–49 years. During 2011–2012, the standard of reported giardiasis per 100,000 peopling was highest in children aged 1–4 years (16.4) and 5–9 years (8.4) followed ~ the agency of adults aged 40–44 years (6.3) and 45–49 years (6.2). Rates were lowest amidst adults aged ≥80 years (2.7 by means of 100,000 population).

During 2011–2012, a gross amount of 18,437 (57.7%) patients were male animal and 13,354 (41.8%) were female; 190 (0.6%) were missing given conditions on sex (Table 2). The more than half of cases for which data forward race were available occurred among whites, followed ~ the agency of blacks, and Asians/Pacific Islanders (Table 2). However, premises on race were not included notwithstanding 41.2% of total annual cover reports. Although 6.5% (2,074 of 16,590) of patients were identified viewed like Hispanic, data on ethnicity were lacking with respect to 48.1% of total annual covering reports.

Analysis of rates by years of discretion and sex showed that giardiasis rates were higher amid males in almost every age arrange (Figure 4). This difference was principally pronounced among males aged 45–49 years. However, in persons having lived 65–69 years, rates were superficially higher among females than males (5.1 versus 4.9 per 100,000 populousness).

Date of symptom onset was reported because 17,105 (53.5%) of the 31,981 cases for the period of 2011–2012. The number of cases ~ dint of. symptom onset peaked in late July to seasonably August (n = 1,075), which was 2.2 times higher than the lowest number of cases ~ means of symptom onset in February (n = 480) (Figure 5).


National giardiasis surveyorship data are critical in assessing the malady prevalence and epidemiologic characteristics of giardiasis in the United States. Following a approximative decline in case reports during 1996–2001, the reckon of case reports and disease rates stabilized for the time of 2002–2010, coinciding with the disorder becoming nationally notifiable in 2002 (Figure 1) (30–34). For the primary time in 10 years, giardiasis rates crop out to be decreasing. Possible reasons by reason of the decreased rates during 2011–2012 force include changes in transmission of indisposition caused by Giardia, a decreased significance on giardiasis surveillance in public health agencies, the 2011 change in particular occurrence definition clarifying that clinical symptoms are essential for categorizing giardiasis cases as confirmed, increased uptake of strategies to impoverish waterborne transmission (e.g., implementation of EPA’s Ground Water Rule to expertness contamination of public ground water systems (40), or a complot of these factors.

The last general surveillance data were published in 2009–2010 (34). Since blazon of that data, rates have declined athwart all regions. Giardiasis rate reductions were ~ly pronounced in the Midwest, where rates declined from 10.3 and 11.4 by means of 100,000 population in 2009 and 2010 to 6.6 and 5.8 in 2011 and 2012. As in anterior years, rates were highest in boreal states, and Vermont reported the highest charge for the last 7 years. The geographic differences puissance suggest actual regional differences in giardiasis transferrence, or they might reflect variation in care capacity across states. Although giardiasis is a nationally notifiable infirmity, six states did not report giardiasis during 2011–2012. The number of states that do not report giardiasis cases has increased from four to six states completely the past 2 years (34). This represents the largest include of nonreporting states since giardiasis became nationally notifiable in 2002(31–34), what one. is a concerning trend, given that giardiasis is the greatest number frequently identified enteric parasite in the United States (1). However, the nonreporting states answer not explain the declines in public rates because rates declined in greatest in quantity states that consistently reported cases.

Giardiasis rates varied ~ dint of. age and sex. The rate of reported giardiasis was higher in males than the fair sex in almost all age groups, specially among adults aged 45–49 years. Compared by previous years, giardiasis rates declined athwart most age groups and both sexes in 2011–2012. Among males and female sex, rates were highest among children aged 1–9 years, which is consistent with previously published reports (30–34). Higher rates in children strength be related to increased recreational moisten exposures, poor hygiene skills, close junction with other potentially infected children in brat-care settings, and lack of foregoing exposure toGiardia, which could set forth them more susceptible to infection and indisposition (41,42). Giardia has been identified frequently as the cause of diarrhea amidst children examined in outpatient clinics (43), and transmittance from ill children to household contacts has been documented in riot investigations (44,45). The sharpest declines were seen in this period of life group as well. The rate mixed children aged 1–4 years declined from 23.5 by 100,000 population in 2009–2010 to 16.4 in 2011–2012, and the appraise among children aged 5–9 years dropped from 12.5 for 100,000 population in 2009–2010 to 8.4 in 2011–2012 (34). No general efforts to prevent person-to-somebody transmission in child-care settings possess occurred that would explain the abuse reductions in young children. Interventions to attenuate drinking water-associated transmission of Giardia (e.g., EPA’s Ground Water Rule) ability have a larger impact on the young, inasmuch as older persons have had more opportunities to have ~ing previously infected with Giardia, which could confer partial protection from reinfection or indicative infection (46,47). Reducing the carriage of this parasite in the give ~ to might, in turn, prevent person-to-person transmittance in settings that foster increased put to hazard for infection, such as child-care centers (18,26).

During 2011–2012, a duplicate increase in giardiasis reporting occurred during summer compared with winter months, by a peak in late July and in season August. This finding is consistent with temporal patterns observed previously in the United States (30–34) and Canada (41), and homogeneous to the seasonal profile of other parasitic and bacterial enteric diseases (e.g., cryptosporidiosis and vibriosis) (48,49). The summer point coincides with increased outdoor activities (e.g., camping and vertigo) that likely increase exposure to contaminated furnish with ~. Transmission associated with outdoor activities is facilitated through the substantial number ofGiardia cysts that can be shed by a single bodily substance (17), the environmental hardiness of the organized being (50), the extended periods of time that cysts can be shed(18), and the moo infectious dose for infection (16).

Drinking sprinkle and calender is a well-documented vehicle for Giardia transmittal. G. intestinalis was the unmarried most frequently identified pathogen in tot~y drinking water outbreaks reported in the United States for the time of 1971–2006, responsible for 28% of completely outbreaks with an identified etiology (3). Untreated drinking water has been identified as a expose to danger factor for sporadic giardiasis in the United States (51,52) and New Zealand (24). Groundwater can be particularly risky if acquired from not well constructed or maintained wells that potency have been subject to surface irrigate contamination.

Both treated and untreated recreational shed ~ also have been implicated as vehicles of giardiasis transmittal. During 1999–2008, Giardia was identified considered in the state of a causal agent of eight (3.5%) of 228 reported recreational supply with ~ -associated gastroenteritis outbreaks (53). In studies of sporadic giardiasis, swallowing water while swimming and recreational juxtaposition with fresh water were both dare to undertake factors for contracting Giardia (22,24). Giardia be able to be frequently detected in fecal matter in pools (54), and transmission has been documented mixed diapered children who use swimming venues regularly (45,55,56).

Reported foodborne outbreaks of giardiasis esteem generally been caused by direct pollution by an infected food handler (57,58) or fowl of the air contamination of food (59). However, foodborne outbreaks of giardiasis are infrequently reported in the United States. During 2000–2010, <1% of foodborne outbreaks by an identified etiology was attributed to Giardia (59). Infections from pollution of widely distributed foods (e.g., novel produce) might be difficult to discover. A recent study of Canadian effect showed that 1.8% of precut salad and leafy grass-plot samples were contaminated with Giardia (60), and a study of separate giardiasis in England identified eating lettuce like a risk factor for giardiasis (22). The conversion to an act of reclaimed wastewater for irrigation is associated by the finding ofGiardia cysts on fresh bring out (61), highlighting the importance of using noncontaminated irrigation water to prevent foodborne disease.

Person-to-human frame transmission of Giardia also occurs. Persons attending or moving in child-care settings or those who acquire close contact with persons with giardiasis are at increased hazard for being infected (51,52,62,63). Exposure to feces end handling diapers and poor hygiene, specially after toileting, in child-care settings puissance contribute to increased risk (20,55).

Although G. intestinalis infects one as well as the other humans and animals, the role of zoonotic transmittal to humans and the importance of denizen of the deep contamination of food and water are vital principle reexamined in light of advances in corpuscular epidemiology. Giardia has been detected in parsimoniously all classes of vertebrates, including pertaining to home animals and wildlife (64), but molecular characterization of G. intestinalis has identified with reference to something else species-specific genetic assemblages. Humans are merely infected with assemblages A and B, that can sometimes be found in other animals. However, animals are usually infected with other species-specific assemblages (64). Epidemiologic data implicating wildlife, cattle, and pets like sources of human-pathogenic Giardia assemblages are limited, and tools and materials from molecular studies of G. intestinalis assemblages and subtypes glance at that the risk of zoonotic transferrence is not as high as antecedently thought (15). No molecular data are reported to CDC surveyorship systems, limiting the ability to be informed the role of zoonotic transmission.

Strategies to bring to want the incidence of giardiasis have focused forward reducing waterborne and person-to-living body transmission (Box). The low infectious dose of Giardia, protracted shedding of cysts, and diminish chlorine tolerance make it ideally suited for transmission through these pathways. The Environmental Protection Agency (EPA) enacted a sequence of rules designed to prevent pathogens in surface water sources from contaminating drinking sprinkle and calender systems (65,66,67,68). These regulations potency have contributed to a decrease in the amount to of giardiasis outbreaks associated with community drinking water systems (3). In 2006, EPA finalized the Ground Water Rule to application contamination of public ground water (well) systems, what one. is likely to reduce the designate by ~ of groundwater-associated outbreaks of giardiasis (40). For recreational wet, proper pool maintenance (i.e., enough disinfection, filtration, and recirculation of wet) and excluding children with diarrhea from pools should grow less transmission through treated recreational water. Person-to-bodily substance transmission of Giardia is difficult to hinder in a systematic fashion, particularly in brat-care settings (63). Adherence to appropriate pollution control policies (e.g., exclusion of children iniquitous with diarrhea, hand washing, diaper changing, and disunion of ill children from well children) is recommended ~ the sake of controlling giardiasis and other enteric pathogens in these arrange settings (69).


The findings in this relation are subject to at least five limitations. First, contingency reports lack data on exposure relation and often have incomplete data in c~tinuance race and ethnicity; thus, it was not likely to evaluate the contributions of exposures or confound racial or ethnic groups at increased dare to undertake for giardiasis. Second, incomplete data ~ward symptom onset date could have led to every inaccurate representation of the seasonal apportionment of cases. Third, incidence of giardiasis is that may be liked to be underestimated by these public surveillance data because of underreporting (e.g., not every part of persons infected with Giardia are symptomatic, persons who are symptomatic do not eternally seek medical care, health-care providers act not always include laboratory diagnostics in their evaluation of nonbloody diarrheal diseases, and box reports are not always completed as being positive laboratory results or forwarded to general health officials). Fourth, the 2011 particular occurrence definition clarification that symptoms should have ~ing present for a case to have ~ing confirmed might limit direct rate comparisons by previous years. Finally, giardiasis is not a reportable ailment in all states, which can show the way to an incomplete picture of its geographic arrangement and an underestimation or overestimation of general incidence rates.

Future Directions

Although giardiasis is the ~ly common enteric parasitic infection in the United States, gaps in comprehension of its epidemiology still exist. Methods to improve reporting contain encouraging health-care providers to consider and specifically request testing for Giardia in the workup of gastrointestinal indisposition, and encouraging health-care providers and laboratories to improve reporting of cases to jurisdictional soundness departments. Improved case investigations, geospatial studies, serosurveys, and the appliance of molecular tools would enhance discursive faculty of the epidemiology of giardiasis. The more than half of data on giardiasis transmission comes from affray investigations; however, the overwhelming majority of reported giardiasis cases occur sporadically. During 2011–2012, <2% of reported giardiasis cases was associated through outbreaks. Many giardiasis outbreaks associated through drinking water occur (3), but the relating to contributions of waterborne, foodborne, person-to-somebody, and animal-to-person transmission are not well understood, especially since sporadic cases. Whether the geographic variability famed in this report reflects actual differences in transmission patterns and disease burden versus diagnosis and reporting artifacts is unclear; in whatever manner, the sharp decline in rates in the Midwest is likely because of a regional decrease in transmittance.

Future research is needed to hinder elucidate the sources of nonoutbreak associated giardiasis infections. Ecologic studies could characterize the potential contributions of private wells, septic systems, put on shore application of biosolids (organic matter recycled from sewage), and agricultural operations in giardiasis transmission. Infected persons can shed Giardia concerning several weeks, and symptoms are inconstant; however, until recently, no reliable serologic assays for Giardiahave been suitable, and no population studies of Giardia seroprevalence bear been conducted. With recent laboratory advances (70), of that kind studies might now be feasible and would grant substantially to understanding of the success of giardiasis in the United States. Enhanced genotyping methods would be augmented knowledge of the molecular epidemiology of Giardia, including elucidating the consequence of zoonotic transmission. Molecular methods moreover could be used to assist the community health officials in linking cases sharing general transmission routes, which could lead to increased ebullition detection. These tools, combined with traditive epidemiology and surveillance, would improve notion of giardiasis risk factors and make known to future prevention strategies. Although recent studies mark a potential for chronic sequelae from giardiasis (9–14), extra research is needed to further improve idea of the prevalence and scope of these provisions.


For the first time from the time of 2002, giardiasis rates appear to subsist decreasing. Despite this decrease, giardiasis dead body the most commonly reported intestinal flattering infection in the United States. National surveyorship data can be used to mentor the revision, updating, and expansion of freedom from disease communication efforts and other public freedom from disease interventions to prevent and control giardiasis. Federal, glory, and local health agencies can application giardiasis surveillance data to help illustrate the epidemiology of giardiasis in the United States, settle public health priorities for giardiasis hindrance, target health communication messages, and design open health interventions to prevent the transferrence of Giardia. Additional information with reference to giardiasis is available at


This sound is based, in part, on contributions ~ dint of. Michele C. Hlavsa, epidemiologist, Division of Foodborne, Waterborne, and Environmental Diseases, and legal power surveillance coordinators Ruth Ann Jajosky, DMD, and Willie Anderson, Office of Surveillance, Epidemiology, and Laboratory Services, CDC.


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