The costs of registry-based immunization interventions.

BACKGROUND: Part of the payoff of immunization registries may be to lower costs of immunization intervention. However, registry-based intervention costs have not been evaluated in a community setting. METHODS: The purpose of this study was to prospectively measure the cost of three equally effective registry-based interventions, evaluate how the size of the targeted population affects cost estimates, and compare these results with previously reported studies. A total of 3050 children aged <12 months were randomized to one of four study arms: (1) computer-generated telephone messages (autodialer), (2) outreach worker, (3) autodialer with outreach worker backup, or (4) usual care. The cost data collected included capital equipment, supplies, travel, and personnel. RESULTS: Monthly costs of the three registry-based intervention types were (1) autodialer, $1.34 per child; (2) outreach worker, $1.87 per child, and (3) combination, $2.76 per child. Personnel costs represented the majority of incremental costs for all three interventions. Increasing the number of children targeted sharply decreased the cost per child for the autodialer but had only a modest effect on outreach costs. The monthly costs for outreach were substantially lower than previously reported for nonregistry-based interventions in part because of differences in the number of children who were followed up. Monthly costs for the autodialer intervention were slightly higher than previously reported, but several published studies excluded important costs. CONCLUSIONS: By facilitating the management of a larger cohort of children, some registry-based immunization interventions appear to be less costly than nonregistry interventions. Further work is needed to establish whether registry maintenance costs may be recouped in part by these savings.

Vaccination coverage and physician distribution in the United States, 1997.

BACKGROUND: How many physicians are needed in the United States and how they should be allocated geographically and among specialties has been the subject of intense debate, a debate that has often focused more on costs to third-party payers and government than on benefits to health. Child health is a central aspect of public health, and immunization is one of its most cost-effective and easily measured interventions. OBJECTIVE: To examine the association of immunization rates and delivery characteristics with the distribution of child health physicians in the United States in 1997. DESIGN: Cross-sectional ecological study, using the state as the unit of analysis, immunization rates and delivery characteristics (from the National Immunization Survey) as the main outcome measures, concentration of the principal physician specialties providing routine care to children (pediatric, family, and general physicians from the American Medical Association Masterfile) as the main risk factor, while controlling for demographic and economic factors (from the Bureau of the Census and other sources). RESULTS: Of the 96 689 physicians providing routine care to children, 37% were pediatric, 49% family, and 14% general physicians. Higher rates of vaccination, private sector vaccination, and increased numbers of public and private vaccination sites were all associated with the concentration of pediatricians but not of family or general physicians. The distribution of pediatricians was strongly associated with the distribution of residency positions. CONCLUSIONS: Pediatrician distribution is a strong correlate to immunization rates and delivery characteristics. Opportunities to affect pediatrician distribution may exist with allocation of residency positions.

Intussusception among infants given an oral rotavirus vaccine.

BACKGROUND: Intussusception is a form of intestinal obstruction in which a segment of the bowel prolapses into a more distal segment. Our investigation began on May 27, 1999, after nine cases of infants who had intussusception after receiving the tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV) were reported to the Vaccine Adverse Event Reporting System. METHODS: In 19 states, we assessed the potential association between RRV-TV and intussusception among infants at least 1 but less than 12 months old. Infants hospitalized between November 1, 1998, and June 30, 1999, were identified by systematic reviews of medical and radiologic records. Each infant with intussusception was matched according to age with four healthy control infants who had been born at the same hospital as the infant with intussusception. Information on vaccinations was verified by the provider. RESULTS: Data were analyzed for 429 infants with intussusception and 1763 matched controls in a case-control analysis as well as for 432 infants with intussusception in a case-series analysis. Seventy-four of the 429 infants with intussusception (17.2 percent) and 226 of the 1763 controls (12.8 percent) had received RRV-TV (P=0.02). An increased risk of intussusception 3 to 14 days after the first dose of RRV-TV was found in the case-control analysis (adjusted odds ratio, 21.7; 95 percent confidence interval, 9.6 to 48.9). In the case-series analysis, the incidence-rate ratio was 29.4 (95 percent confidence interval, 16.1 to 53.6) for days 3 through 14 after a first dose. There was also an increase in the risk of intussusception after the second dose of the vaccine, but it was smaller than the increase in risk after the first dose. Assuming full implementation of a national program of vaccination with RRV-TV, we estimated that 1 case of intussusception attributable to the vaccine would occur for every 4670 to 9474 infants vaccinated. CONCLUSIONS: The strong association between vaccination with RRV-TV and intussusception among otherwise healthy infants supports the existence of a causal relation. Rotavirus vaccines with an improved safety profile are urgently needed.

A large rubella outbreak with spread from the workplace to the community.

CONTEXT: Childhood vaccination has reduced rubella disease to low levels in the United States, but outbreaks continue to occur. The largest outbreak in the past 5 years occurred in Nebraska in 1999. OBJECTIVES: To examine risk factors for disease, susceptibility of the risk population, role of vaccine failure, and the need for new vaccination strategies in response to the Nebraska rubella outbreak. DESIGN, SETTING, AND PATIENTS: Investigation of 83 confirmed rubella cases occurring in Douglas County, Nebraska, between March 23 and August 24, 1999; serosurvey of 413 pregnant women in the outbreak locale between October 1998 and March 1999 (prior to outbreak) and April and November 1999 (during and after outbreak). MAIN OUTCOME MEASURES: Case characteristics, compared with that of the general county population; area childhood rubella vaccination rates; and susceptibility among pregnant women before vs during and after the outbreak. RESULTS: All 83 rubella cases were unvaccinated or had unknown vaccination status and fell into 3 groups: (1) 52 (63%) were young adults (median age, 26 years), 83% of whom were born in Latin American countries where rubella vaccination was not routine. They were either employed in meatpacking plants or were their household contacts. Attack rates in the plants were high (14.4 per 1000 vs 0. 19 per 1000 for general county population); (2) 16 (19%), including 14 children (9 of whom were aged <12 months) and 2 parents, were US-born and non-Hispanic, who acquired the disease through contacts at 2 day care facilities (attack rate, 88.1 per 1000); and (3) 15 (18%) were young adults (median age, 22 years) whose major disease risk was residence in population-dense census tracts where meatpacking-related cases resided (R(2) = 0.343; P<.001); 87% of these persons were born in Latin America. Among pregnant women, susceptibility rates were 13% before the outbreak and 11% during and after the outbreak. Six (25%) of 24 susceptible women tested were seropositive for rubella IgM. Rubella vaccination rates were 90.2% for preschool children and 99.8% for school-aged children. CONCLUSIONS: A large rubella outbreak occurred among unvaccinated persons in a community with high immunity levels. Crowded working and living conditions facilitated transmission, but vaccine failure did not. Workplace vaccination could be considered to prevent similar outbreaks. JAMA. 2000;284:2733-2739.

The status of immunization measurement and feedback in the United States.

BACKGROUND: A large body of scientific and programmatic data has demonstrated that provider measurement and feedback raises immunization coverage. Starting in 1995, Congress required that all states measure childhood immunization coverage in all public clinics, and federal grant guidelines encourage private practice measurements. OBJECTIVES: To determine state immunization measurement rates and examine risk factors for high rates. METHODS: Review of 1997 state reports, with correlation of measurement rates to birth cohort and provider numbers, public/private proportions, and vaccine distribution systems. RESULTS: Of the 9505 public clinics, 48% were measured; 4 states measured all clinics; 29 measured a majority. Measurement rates were highest for Health Department clinics (67%), lower for community/migrant health centers (39%), and lowest for other clinics (22%). Rates were highly correlated among categories of clinics (r>+0.308, P<.03), and the fewer the clinics, the higher the measurement rates (r = -0.351, P =. 01), but other factors were not significant. Of the 41,378 private practices, 6% were measured; no state measured all its practices; 1 measured a majority. Private practice measurement rates were not correlated to public clinic measurement rates or other factors examined. Of the 50,883 total providers, 14% were measured; no state measured all providers; 2 measured a majority. A trend toward higher measurement rates was found in states with fewer providers (r = -0. 266, P =.06). CONCLUSIONS: Three years after the congressional mandate, only a minority of public clinics and very few private practices had their immunization coverage measured. Greater efforts will be needed to assure implementation of the intervention. Arch Pediatr Adolesc Med. 2000;154:832-836

How much time is spent on well-child care and vaccinations?

CONTEXT: Because well-child care represents the most important prevention opportunity in the health care system, a growing number of activities and indicators have been proposed for it. OBJECTIVE: To measure the time spent in the various components of well-child care. DESIGN: Time-and-motion study. SETTING: Five private pediatric practices and 2 public providers in Rochester, NY. PARTICIPANTS: One hundred sixty-four children younger than 2 years. MAIN OUTCOME MEASURE: Duration of family's encounters with the primary care provider (physician or nurse practitioner), nurse, and other personnel. RESULTS: The median encounter times and their component parts in minutes were: (1) primary care provider, 16.3 (physical examination, 4.9; vaccination discussion, 1.9; discussion of other health issues, 9.5; vaccination administration, 0); (2) nurse, 5.6 (physical examination, 3.5; vaccination discussion, 0; other health discussion, 0; vaccine administration, 1.6); and (3) other personnel, 0 for all categories. Public provider setting, African American race of the child, and administration of 4 vaccinations were significantly associated with an increase (3-4 minutes) in the duration of the primary care provider encounter. Only 8 (5%) of families read vaccine information materials. CONCLUSIONS: Depending on whether a child makes the usual 3 or recommended 6 number of well-child visits, the total time of well-child care is 45 to 90 minutes during the first year of life and declines to less than 30 minutes per year thereafter as the number of recommended visits diminish. Because high-risk children make half as many well-child care visits as other children, a 3 to 4 minute increase in encounter time is insufficient to provide them with the same level of care as other children.

Changes in clinic vaccination coverage after institution of measurement and feedback in 4 states and 2 cities.

BACKGROUND: Since 1995, states and jurisdictions receiving federal immunization funds have been required to perform annual measurements of vaccination coverage in their public clinics, based on data from Georgia where clinic coverage increased after the institution of a measurement and feedback intervention. OBJECTIVE: To determine if clinic vaccination coverage improved in localities that used the Georgia intervention model. DESIGN: Retrospective examination of clinic vaccination coverage data. PARTICIPANTS: Children aged 19 to 35 months enrolled in clinics in localities that had applied the intervention for 4 years or longer. INTERVENTION: The Georgia intervention model: assessment of clinic vaccination coverage, feedback of the information to the clinic, incentives to clinics, and promotion of exchange of information among clinics (AFIX). MAIN OUTCOME MEASURE: Change in median clinic coverage rates, based on the primary (4-3-1) vaccine series, with comparison to results of the National Immunization Survey. RESULTS: Four states and 2 cities that had applied the AFIX intervention for 4 years or longer were identified. The number of clinic records reviewed annually was 4639 to 18000 in 73 to 116 clinics for states, and 714 to 5276 in 8 to 25 clinics for cities. Median clinic coverage rose in all localities: Missouri, 44% (1992) to 93% (1997); Louisiana, 61% (1992) to 83% (1997); Colorado, 55% (1993) to 75% (1997); Iowa, 71% (1994) to 89% (1997); Boston, Mass, 41% (1994) to 79% (1997); and Houston, Tex, 28% (1994) to 84% (1997). The increase in clinic coverage exceeded that of the general population in 5 localities and was identical in the sixth. The average annual coverage rise attributable to the intervention was +5 percentage points per year (Georgia, +6 per year). The average crude direct program cost was $49533 per locality per year. CONCLUSION: The Georgia intervention model (AFIX) can be reproduced elsewhere and is associated with improvements in clinic vaccination coverage.

Does reminder-recall augment the impact of voucher incentives on immunization rates among inner-city infants enrolled in WIC? Special Supplemental Program for Women, Infants, and Children.

Inner-city infants (n = 565) enrolled in the WIC program were randomly assigned at 6 months of age to either of 2 groups: (1) voucher incentive (frequency of issuance of food vouchers based on immunization status) plus reminder-recall (calls and/or letters to families of under-vaccinated children) or (2) voucher incentive alone. At 12 months, both groups' immunization levels were high and not significantly different: 80% +/- 4% versus 79% +/- 5% (P =.749).

Impact of a large-scale immunization initiative in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)

CONTEXT: Inner-city immunization rates have lagged behind those in other areas of the country. OBJECTIVE: To evaluate the impact of an initiative linking immunization with distribution of food vouchers in the inner city. DESIGN: Retrospective analysis of immunization data gathered in 1996 and 1997. SETTING: Nineteen Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) sites serving 30% of the Chicago, III, birth cohort. PARTICIPANTS: A total of 16581 children 24 months old or younger. INTERVENTIONS: Voucher incentives (varying frequency of food voucher issuance based on immunization status) and assessment of immunization status and referral to immunization provider. MAIN OUTCOME MEASURES: Age-appropriate immunization rates and WIC enrollment rates. RESULTS: During the 15-month period of evaluation, immunization rates increased from 56% to 89% at sites performing voucher incentives. The proportion of children needing voucher incentives declined from 51% to 12%. Sites performing assessment and referral, but not providing voucher incentives, showed no evidence of improvement in immunization coverage. No difference was observed in enrollment rates between sites performing voucher incentives and those that did not. CONCLUSION: Applied in a large-scale, programmatic fashion, voucher incentives in WIC can rapidly increase and sustain high childhood immunization rates in an inner-city population.

The impact of interventions by a community-based organization on inner-city vaccination coverage: Fulton County, Georgia, 1992-1993.

OBJECTIVE: To evaluate the impact of interventions by a community-based organization on immunization rates. DESIGN: Controlled community intervention trial. SETTING AND PARTICIPANTS: Children aged 3 to 59 months in Fulton County, Georgia, who were patients of 1 of 4 public clinics (clinic based), or residents of 1 of 9 inner-city communities (residence based). INTERVENTIONS: (1) Clinic-based intervention included monthly review of clinic vaccination records to identify undervaccinated children followed by contact with family (reminder-recall strategy); (2) residence-based intervention included door-to-door assessment and education campaigns followed by mobile van vaccinations, temporary on-site vaccination stations, free child care and transportation to providers, incentives of food and baby products, focus groups, and coalitions with local organizations (community saturation with vaccination messages and opportunities). OUTCOME MEASURES: Change in vaccination rates after 1 year based on clinic record reviews and population surveys. RESULTS: For clinic-based intervention, series completion rates improved from 43% (87/204) to 58% (99/170) in intervention clinics (P=.003), while rates in control clinics did not change from the baseline of 52% (81/157 to 78/150), for a net difference between intervention and control arms of +15 percentage points (P=.046). For residence-based intervention, age-appropriate vaccination rates improved from 44% (154/347) to 61% (260/429) in intervention communities (+17 percentage points; P<.001) compared with improvement of 44% (78/178) to 58% (129/221) for control communities (+14 percentage points; P=.004), but the difference between arms was not significant (+3 percentage points, P=.78). CONCLUSIONS: Reminder-recall activities by the community-based organization improved vaccination rates in intervention clinics compared with control clinics. A statistically significant impact on vaccination rates could not be detected for residence-based interventions by the community-based organization.

Impact of measurement and feedback on vaccination coverage in public clinics, 1988-1994.

OBJECTIVE: To investigate whether a reported rise in vaccination coverage in Georgia public clinics during the period 1988 through 1994 was artifactual or real and, if real, to determine the extent to which the rise could be associated with a program of measurement and feedback. DESIGN: Examination of data from Georgia public clinics, doses-administered records, and National Health Interview Surveys. SETTING/PARTICIPANTS: Children attending Georgia public clinics. INTERVENTION: Measurement of vaccination coverage and feedback to providers. MAIN OUTCOME MEASURE: Vaccination coverage rates. RESULTS: For the period 1988 through 1994, 136 004 Georgia public clinic vaccination records for children 21 to 23 months of age were reviewed. Median series-completion rates at public clinics rose from 53% to 89%, while indexes of under-vaccination fell: missed opportunities for simultaneous vaccination (6% to 0%), lost contact for more than 12 months (14% to 1%), and first vaccination more than 1 month late (19% to 8%). According to the independent doses-administered database, the proportion of children starting the primary series very late (> or =12 months old) fell from 14% to 6%, and the series-completion index rose from 64% to 83%, suggesting that improvements could not be wholly ascribed to better clinic record keeping. In 1988, vaccination coverage of children 24 months of age in the National Health Interview Survey (NHIS) was 53%, identical to median public clinic coverage in Georgia; in 1993, NHIS coverage was 60%, while median public clinic coverage in Georgia was 90%, suggesting that the rise in coverage in Georgia public clinics exceeded national trends. Patterns within the coverage changes suggest an association with the process of measurement and feedback. CONCLUSIONS: A marked increase in vaccination coverage occurred in Georgia public clinics associated with a program of annual measurement and feedback.

Information as intervention: how Georgia used vaccination coverage data to double public sector vaccination coverage in seven years.

All states are now required by federal law to measure immunization coverage in each public clinic in their jurisdiction once a year. This law is based on data suggesting a twofold increase of immunization coverage in public clinics in Georgia during a seven-year period when the state developed a system for measuring clinic coverage and using these data to stimulate immunization performance. Review of the history of the development of the Georgia system suggests that measurement alone is not sufficient to raise coverage, however. In Georgia, measurement was coupled with a vigorous program of feedback of coverage data, provision of incentives for good performance, and exchange of information among clinics. The Centers for Disease Control and Prevention (CDC) has summarized the Georgia system with the acronym AFIX--Assessment, Feedback, Incentives, eXchange of information--and recommends that all state immunization program managers test and adapt this methodology. The article comments on the development of the Georgia system and describes why CDC believes other states should adopt it.

Measles vaccination levels of children enrolled in WIC during the 1991 measles epidemic in New York City.

OBJECTIVES: This study assessed measles vaccination rates and risk factors for lack of vaccination among preschool children enrolled in the Special Supplemental Food Program for Women, Infants, and Children (WIC) during the 1991 measles epidemic in New York City. METHODS: Children aged 12 to 59 months presenting for WIC certification between April 1 and September 30, 1991, at six volunteer WIC sites in New York City were surveyed. RESULTS: Of the 6181 children enrolled in the study, measles immunization status was ascertained for 6074 (98%). Overall measles coverage was 86% (95% confidence interval [CI] = +/- 1%) and at least 90% by 21 months of age (95% CI = +/- 1%). Young age of the child, use of a private provider, and Medicaid as a source of health care payment were risk factors for lack of vaccination (P < .001). CONCLUSIONS: During the peak of a measles epidemic, measles immunization rates were more than 80% by 24 months of age in a sample of WIC children. The ease of ascertaining immunization status and the size of the total WIC population underscore the importance of WIC immunization initiatives.

The immunization of children enrolled in the Special Supplemental Food Program for Women, Infants, and Children (WIC). The impact of different strategies.

OBJECTIVE: To assess the impact of different interventions to increase measles vaccination coverage among preschool children enrolled in the Special Supplemental Food Program for Women, Infants, and Children (WIC). DESIGN: Public health intervention trial. SETTING: Six volunteer WIC sites in New York City. STUDY PARTICIPANTS: Children aged 12 to 59 months presenting for WIC certification between April 1 and September 30, 1991, who were eligible for measles vaccination. INTERVENTIONS: Two WIC sites were assigned at random to one of three immunization strategies: (1) escort: child was escorted to a nearby pediatric clinic for immunization; (2) voucher incentive: the family returned monthly, rather than every 2 months, to pick up WIC food vouchers until the child was immunized; or (3) referral: the family was passively referred for immunization. MAIN OUTCOME MEASURE: Proportion of eligible children receiving measles vaccination. RESULTS: Of children eligible for measles immunization, 74% (618/836) were immunized. Children at escort sites were 5.5 times (relative risk [RR] = 5.5; 95% confidence interval [CI], 3.7 to 8.1) and those at voucher incentive sites were 2.9 times (RR = 2.9; 95% CI, 1.9 to 4.5) more likely to be immunized than children at referral sites. Children were immunized more rapidly at escort sites (median, 14 days) and voucher incentive sites (median, 26 days) than at referral sites (median, 45 days; P < .001). CONCLUSIONS: Both escort and voucher incentive models resulted in more children being immunized more rapidly than passive referral. Because of ease of administration, voucher incentives may be a more suitable immunization intervention for use at WIC sites, with addition of escort where feasible.

Outbreaks of summer rotavirus linked to laboratory practices. The National Rotavirus Surveillance System.

In temperate regions rotavirus diarrhea is a disease of the cooler months of the year, but little is known about its patterns in the summer. We report on the first year of national surveillance of rotavirus, during which we actively investigated patterns of summer activity. We obtained data on rotavirus testing from 85 laboratories in 48 states, conducted a survey of their testing practices and retested for confirmation positive specimens from laboratories reporting high rates of positivity during the summer. During 1989 participating laboratories reported 4011 specimens tested for rotavirus during July and August, of which 436 (11%) were said to be positive. Most laboratories reported low rates of positivity during these months (median percent positive, 3), but five had very high rates of summer positivity (> 30%). These five laboratories were geographically separated, and neighboring laboratories showed little rotavirus activity. Positive specimens submitted by four of these centers with high rates of summer rotavirus could not be confirmed. A survey of laboratory methods found one commercial assay (TestPack) and two laboratory practices (failure to use controls and involvement of more than six technicians in the testing process) to be associated with high rates of summer positivity. Moderate rates of positivity (11 to 30%) were fond frequently in the southwest during July and August; reference testing of specimens from these laboratories confirmed positivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Laboratory-based surveillance for rotavirus United States, January 1989-May 1991.

Geographic and temporal trends of rotavirus detections in the United States for the period January 1989-May 1991 were determined by analyzing data reported monthly by 47 virology laboratories participating in the North American Rotavirus Surveillance System. Reports included complete information on the number of specimens tested, the number of test results positive for rotavirus, and the method used to detect rotavirus. Consistent trends in regional and geographic area were identified, with distinctly different peaks of rotavirus activity in the western and eastern states. Each year in the western states, rotavirus activity began in November and peaked in December-January, whereas in the eastern states activity began in January and peaked in February-March. These differences do not correlate with obvious trends in strain variation of rotavirus and remain unexplained. Unexpected reporting of summer rotavirus activity by some laboratories in 1989 was traced to the use of a single diagnostic kit and to two questionable laboratory practices: having more than six medical technologists perform the test and failure to use controls with the test. Laboratory-based surveillance of rotavirus activity has proven to be useful in identifying and correcting problems in laboratory methods for detecting rotavirus and will be a sensitive means for monitoring coverage of the rotavirus vaccine now being developed.

Estimates of morbidity and mortality rates for diarrheal diseases in American children.

Although the importance of diarrhea as a prime cause of morbidity and death in developing countries is well recognized, the disease burden in the United States has never been thoroughly examined. We have prepared national estimates of the annual number of cases of diarrhea in children less than 5 years of age and of the outcome, measured in terms of visits to a physician, hospitalizations, and deaths. The annual number of diarrheal episodes was estimated by reviewing longitudinal studies of childhood diarrhea conducted in the United States and extrapolating these data to the nation. Estimates of physician visits, hospitalizations, and deaths were prepared from a variety of national data sources. We estimate that 16.5 million children less than 5 years of age have between 21 and 37 million episodes of diarrhea annually. Of these, 2.1 to 3.7 million episodes lead to a physician visit, a total of 220,000 patients are hospitalized, and 325 to 425 children die. The major cost of diarrhea lies in the high numbers and cost of hospitalizations, because approximately 10.6% of hospitalizations in this age group are for diarrhea. Diarrheal deaths occur in relatively small numbers, are more common in the South and among black persons, are potentially avoidable, and could represent as much as 10% of the preventable postneonatal infant death in the United States. These estimates underscore the extensive burden of diarrheal illness in children in the United States and suggest that interventions to prevent disease or decrease its severity could be cost-effective.

Recommendations for collection of laboratory specimens associated with outbreaks of gastroenteritis.

Recent discoveries have implicated a number of "new" (i.e., previously unrecognized) infectious agents as important causes of outbreaks of gastroenteritis. Unfortunately, the ability to detect these agents in an outbreak can be limited by two factors: 1) the lack of appropriate assays-many of which are still in developmental stages and are not readily available to clinical laboratories, and 2) inadequately or improperly collected specimens. At CDC, many newly developed assays are being used for research and for outbreak investigations. The information in this report is especially intended for public health agencies that collaborate with CDC in investigating outbreaks of gastroenteritis. The report provides an update on guidelines and recommendations for the proper collection of specimens to be sent to CDC, gives general background information concerning some recently discovered pathogens, lists some of the tests available at CDC, and provides a list of CDC contacts. The guidelines and the general information provided on causes of outbreaks of gastroenteritis can be also used by public health workers for investigations when specific testing is available and appropriate.

Six-year retrospective surveillance of gastroenteritis viruses identified at ten electron microscopy centers in the United States and Canada.

To identify the prevalence, seasonality and demographic characteristics of patients with viral gastroenteritis, we reviewed 6 years of retrospective data on viral agents of gastroenteritis screened by electron microscopy at 10 centers in the United States and Canada. From 52,691 individual electron microscopic observations, a virus was detected in 16% of specimens, and the yearly positive detection rate among centers ranged from 8 to 34%. Rotavirus was the agent most commonly observed (26 to 83%), followed by adenoviruses (8 to 27%, respiratory and enteric combined), and small round viruses (SRVs) (0 to 40%) which were second most common at two of the centers. Rotavirus and astrovirus detections occurred more often in the winter but seasonal trends in detection were not apparent for the other viruses. Of all astroviruses detected 64% were found in infants (less than 1 year); unlike the other agents studied SRVs were detected in a large percentage of infants (48%) and older children and adults (20%). Among hospitalized patients a majority of all astroviruses, caliciviruses and SRVs were detected 7 days or more after admission in contrast to both rotaviruses and adenoviruses which were more likely to be detected earlier. The data suggest that SRVs are common agents of gastroenteritis and may be important causes of nosocomial infections. Because of the relative insensitivity of direct electron microscopy as a screening method for SRVs, astroviruses and caliciviruses, these data probably underestimate the true prevalence of disease caused by these agents.

Variabilidad estacional mundial de las infecciones por rotavirus / Global seasonality of rotavirus infections

Global seasonability of rotavirus infections