Evaluating the long-term persistence of Bacillus spores on common surfaces.

Bacillus spores resist inactivation, but the extent of their persistence on common surfaces is unclear. This work addresses knowledge gaps regarding biothreat agents in the environment to reduce uncertainty in risk assessment models. Studies were conducted to investigate the long-term inactivation of Bacillus anthracis and three commonly used surrogate organisms - B. cereus, B. atrophaeus and B. thuringiensis on three materials: laminate countertop, stainless steel and polystyrene Petri dishes. Viable spores were measured at 1, 30, 90, 196, 304 and 1038 days. Twelve different persistence models were fit to the data using maximum likelihood estimation and compared. The study found that (1) spore inactivation was not log-linear, as commonly modelled; (2) B. thuringiensis counts increased at 24 h on all materials, followed by a subsequent decline; (3) several experiments showed evidence of a 'U' shape, with spore counts apparently decreasing and then increasing between 1 and 304 days; (4) spores on polystyrene showed little inactivation; and (5) the maximum inactivation of 56% was observed for B. atrophaeus spores on steel at 196 days. Over the range of surfaces, time durations and conditions (humidity controlled vs. uncontrolled) examined, B. thuringiensis most closely matched the behaviour of B. anthracis.

Antibacterial and antiviral effectiveness of two household water treatment devices that use monobrominated hydantoinylated polystyrene.

Many different household water treatment (HWT) methods have been researched and promoted to mitigate the serious burden of diarrheal disease in developing countries. However, HWT methods using bromine have not been extensively evaluated. Two gravity-fed HWT devices (AquaSure™ and Waterbird™) were used to test the antimicrobial effectiveness of HaloPure® Br beads (monobrominated hydantoinylated polystyrene) that deliver bromine. As water flows over the beads, reactive bromine species are eluted, which inactivate microorganisms. To assess log10 reduction values (LRVs) for Vibrio cholerae, Salmonella enterica Typhimurium, bacteriophage MS2, human adenovirus 2 (HAdV2), and murine norovirus (MN), these organisms were added to potable water and sewage-contaminated water. These organisms were quantified before and after water treatment by the HWT devices. On average, 6 LRVs against Vibrio were attained, as well as 5 LRVs against Salmonella, 4 LRVs against MS2, 5 LRVs against HAdV2, and 3 LRVs against MN. Disinfection was similar regardless of whether sewage was present. Polymer beads delivering bromine to drinking water are a potentially effective and useful component of HWT methods in developing countries.

The joint effects of efficacy and compliance: a study of household water treatment effectiveness against childhood diarrhea.

The effectiveness of household water treatment (HWT) at reducing diarrheal disease is related to the efficacy of the HWT method at removing pathogens, how people comply with HWT, and the relative contributions of other pathogen exposure routes. We define compliance with HWT as the proportion of drinking water treated by a community. Although many HWT methods are efficacious at removing or inactivating pathogens, their effectiveness within actual communities is decreased by imperfect compliance. However, the quantitative relationship between compliance and effectiveness is poorly understood. To assess the effectiveness of HWT on childhood diarrhea incidence via drinking water for three pathogen types (bacterial, viral, and protozoan), we developed a quantitative microbial risk assessment (QMRA) model. We examined the relationship between log(10) removal values (LRVs) and compliance with HWT for scenarios varying by: baseline incidence of diarrhea; etiologic fraction of diarrhea by pathogen type; pattern of compliance within a community; and size of contamination spikes in source water. Benefits from increasing LRVs strongly depend on compliance. For perfect compliance, diarrheal incidence decreases as LRVs increase. However, if compliance is incomplete, there are diminishing returns from increasing LRVs in most of the scenarios we considered. Higher LRVs are more beneficial if: contamination spikes are large; contamination levels are generally high; or some people comply perfectly. The effectiveness of HWT interventions at the community level may be limited by imperfect compliance, such that the benefits of high LRVs are not realized. Compliance with HWT should be carefully measured during HWT field studies and HWT dissemination programs. Studies of pathogen concentrations in a variety of developing-country source waters are also needed. Guidelines are needed for measuring and promoting compliance with HWT.

Risk reduction assessment of waterborne Salmonella and Vibrio by a chlorine contact disinfectant point-of-use device.

Unsafe drinking water continues to burden developing countries despite improvements in clean water delivery and sanitation, in response to Millennium Development Goal 7. Salmonella serotype Typhi and Vibrio cholerae bacteria can contaminate drinking water, causing waterborne typhoid fever and cholera, respectively. Household water treatment (HWT) systems are widely promoted to consumers in developing countries but it is difficult to establish their benefits to the population for specific disease reduction. This research uses a laboratory assessment of halogenated chlorine beads treating contaminated water to inform a quantitative microbial risk assessment (QMRA) of S. Typhi and V. cholerae disease in a developing country community of 1000 people. Laboratory challenges using seeded well water resulted in log10 reductions of 5.44 (± 0.98 standard error (SE)) and 6.07 (± 0.09 SE) for Salmonella serotype Typhimurium and V. cholerae, respectively. In well water with 10% sewage and seeded bacteria, the log10 reductions were 6.06 (± 0.62 SE) and 7.78 (± 0.11 SE) for S. Typhimurium and V. cholerae, respectively. When one infected individual was contributing to the water contamination through fecal material leaking into the water source, the risk of disease associated with drinking untreated water was high according to a Monte Carlo analysis: a median of 0.20 (interquartile range [IQR] 0.017-0.54) for typhoid fever and a median of 0.11 (IQR 0.039-0.20) for cholera. If water was treated, risk greatly decreased, to a median of 4.1 × 10(-7) (IQR 1.6 × 10(-8) to 1.1 × 10(-5)) for typhoid fever and a median of 3.5 × 10(-9) (IQR 8.0 × 10(-10) to 1.3 × 10(-8)) for cholera. Insights on risk management policies and strategies for public health workers were gained using a simple QMRA scenario informed by laboratory assessment of HWT.

Trends in Michigan early adolescent immunization: 2006-2008.

OBJECTIVES: We have described vaccine coverage of Michigan young adolescents immunized with tetanus, diphtheria, and pertussis; meningococcal conjugate; and human papillomavirus vaccines during 2006-2008. METHODS: We obtained data from the Michigan Care Improvement Registry, a state-based immunization information system that included more than 57 million vaccination records. We examined 3 overlapping cohorts of 11- and 12-year-old children (n > 350 000 in each) to assess temporal trends in vaccination coverage, characteristics of those immunized, funding sources, and vaccination sites. RESULTS: Vaccine uptake increased during 2006 through 2008, peaking in the summer months. More than half of children receiving more than 1 vaccine received the vaccines simultaneously. Older age, receipt of Medicaid, and prior completion of early childhood immunizations were associated with greater odds of vaccination. CONCLUSIONS: Vaccine coverage among Michigan young adolescents is increasing but continues to be relatively low. Coverage of 11- and 12-year-old children may improve with efforts to encourage vaccination at all health care visits, an increase in public funding in support of adolescent vaccination, and continued monitoring of adolescent vaccination levels through school-based assessments.

Linking quantitative microbial risk assessment and epidemiological data: informing safe drinking water trials in developing countries.

Intervention trials are used extensively to assess household water treatment (HWT) device efficacy against diarrheal disease in developing countries. Using these data for policy, however, requires addressing issues of generalizability (relevance of one trial in other contexts) and systematic bias associated with design and conduct of a study. To illustrate how quantitative microbial risk assessment (QMRA) can address water safety and health issues, we analyzed a published randomized controlled trial (RCT) of the LifeStraw Family Filter in the Congo. The model accounted for bias due to (1) incomplete compliance with filtration, (2) unexpected antimicrobial activity by the placebo device, and (3) incomplete recall of diarrheal disease. Effectiveness was measured using the longitudinal prevalence ratio (LPR) of reported diarrhea. The Congo RCT observed an LPR of 0.84 (95% CI: 0.61, 1.14). Our model predicted LPRs, assuming a perfect placebo, ranging from 0.50 (2.5-97.5 percentile: 0.33, 0.77) to 0.86 (2.5-97.5 percentile: 0.68, 1.09) for high (but not perfect) and low (but not zero) compliance, respectively. The calibration step provided estimates of the concentrations of three pathogen types (modeled as diarrheagenic E. coli, Giardia, and rotavirus) in drinking water, consistent with the longitudinal prevalence of reported diarrhea measured in the trial, and constrained by epidemiological data from the trial. Use of a QMRA model demonstrated the importance of compliance in HWT efficacy, the need for pathogen data from source waters, the effect of quantifying biases associated with epidemiological data, and the usefulness of generalizing the effectiveness of HWT trials to other contexts.

Factors associated with hepatitis A vaccination receipt in one-year-olds in the state of Michigan.

The objectives of this study were to determine factors associated with hepatitis A vaccination and to assess overall hepatitis A vaccination coverage levels among one-year-olds in Michigan. The study population was the first hepatitis A vaccination-eligible birth cohort (n = 134 226) enrolled in the Michigan Care Improvement Registry (MCIR) after 2006 recommendations were made to routinely vaccinate all one-year-olds. All children whose first birthday occurred on or between May 1, 2006 and April 31, 2007 were included in the study population. Racial/ethnic minorities had increased odds of receiving the hepatitis A vaccination in Michigan, and Medicaid and WIC status modified this relationship. Fully understanding these relationships will be useful in targeting vaccination outreach and education programs.

Geographic clustering of nonmedical exemptions to school immunization requirements and associations with geographic clustering of pertussis.

School immunization requirements are important in controlling vaccine-preventable diseases in the United States. Forty-eight states offer nonmedical exemptions to school immunization requirements. Children with exemptions are at increased risk of contracting and transmitting vaccine-preventable diseases. The clustering of nonmedical exemptions can affect community risk of vaccine-preventable diseases. The authors evaluated spatial clustering of nonmedical exemptions in Michigan and geographic overlap between exemptions clusters and clusters of reported pertussis cases. Kulldorf's scan statistic identified 23 statistically significant census tract clusters for exemption rates and 6 significant census tract clusters for reported pertussis cases between 1993 and 2004. The time frames for significant space-time pertussis clusters were August 1993-September 1993, August 1994-February 1995, May 1998-June 1998, April 2002, May 2003-July 2003, and June 2004-November 2004. Census tracts in exemptions clusters were more likely to be in pertussis clusters (odds ratio = 3.0, 95% confidence interval: 2.5, 3.6). The overlap of exemptions clusters and pertussis clusters remained significant after adjustment for population density, proportion of racial/ethnic minorities, proportion of children aged 5 years or younger, percentage of persons below the poverty level, and average family size (odds ratio = 2.7, 95% confidence interval: 2.2, 3.3). Geographic pockets of vaccine exemptors pose a risk to the whole community. In addition to monitoring state-level exemption rates, health authorities should be mindful of within-state heterogeneity.

Influenza vaccination coverage: findings from immunization information systems.

BACKGROUND: Beginning with the 2004-05 influenza season, the Advisory Committee on Immunization Practices (ACIP) strengthened their existing encouragement that children aged 6-23 months receive influenza vaccination by creating a formal recommendation. METHODS: Well-functioning sentinel project immunization information systems (IIS) in Arizona (AIIS) and Michigan (MIIS) were used to calculate vaccination coverage among children aged 6-23 months during the 2004-05 influenza season. We calculated 2 measures of vaccination coverage: a) receipt of 1 or more doses of influenza vaccine September 2004-March 2005 and b) receipt of 2 or more doses (ie, fully vaccinated). We compared the dose administration distribution among children needing 1 and 2 doses and by provider type. Coverage by age and timeliness of vaccine doses entered into the IIS were also analyzed. RESULTS: Influenza vaccination coverage levels among children were 30% and 27% in AIIS and MIIS, respectively, for receipt of 1 or more doses; 13% and 11% of children, respectively, were fully vaccinated. Peaks in dose administration among children needing 1 and 2 doses were similar. There were differences in vaccine administration between public and private providers. Coverage was higher among younger children and over 75% of all influenza vaccine doses were entered into the IIS within 30 days after receipt of vaccine. CONCLUSION: Though almost 1/3 of children received 1 or more doses of vaccine in 2 IIS sentinel projects during the first season of the new recommendation, emphasis needs to be placed on increasing the proportion of children fully vaccinated. IIS data can be used for timely monitoring of vaccination coverage assessments.

Meningococcal conjugate vaccine uptake, measured by Michigan's immunization registry.

PURPOSE: To describe the uptake of meningococcal conjugate vaccine (MCV4) in Michigan adolescents following its approval in January 2005, and compare it to the use of meningococcal polysaccharide vaccine (MPSV4) in 2004. METHODS: All available records of meningococcal immunizations given between February 1986 and March 2006 were obtained from the Michigan Childhood Immunization Registry (MCIR), which is used by about 95% of Michigan immunization providers. During late 2005 and early 2006, these records were analyzed by immunization type, administration date, recipient age, and health care provider type (public or private). RESULTS: The MCIR contained 63,253 meningococcal immunizations. A total of 15.2% were given in 2004, 68.8% in 2005, and 10.8% in 2006. In those years, most immunizations occurred in June, July, and August. In 2005, 85.2% were MCV4. In 2004, 17 to 18-year olds received nearly all meningococcal immunizations; in 2005, 11 to 16-year olds received 58.0% of them. Estimates of immunization coverage were 4.0% for 11 to 12-year olds, 3.4% for 13 to 16-year olds, 5.9% for 17 to 19-year olds, and 19% for freshmen entering college. CONCLUSIONS: Compared to 2004, in 2005 there was a large increase in the number of doses administered, with more MCV4 than MPSV4. Patterns of immunization were consistent with the Advisory Committee on Immunization Practices (ACIP) recommendations. Coverage of Michigan adolescents is low, but increased in 2005 compared with 2004.

Immunization information systems national research and evaluation agenda.

Immunization Information Systems (IIS) are operational in most states and are useful in programmatic and clinical assessments. To ensure that IIS reach their technical and usability potential, and to promote their use, we conducted a Delphi survey to develop a national IIS research and evaluation agenda. Experts with a wide range of IIS knowledge were asked to generate research and evaluation topics that document their utility in achieving and sustaining clinical and public health goals. Topics were then collated by the authors into 13 main categories and were ranked by the survey experts in order of importance. Provider perspectives and needs was ranked as the top research priority. Both data quality and technical data exchange also ranked high, as well as increasing provider participation and IIS cost and cost savings. Lower-ranked research priorities included data sharing between states and factors affecting IIS population-based measurements. Development of an IIS research and evaluation agenda allows policy makers to ensure that their decisions coincide with expert views on national priorities and enables researchers to conduct studies addressing topics recognized as nationally important. It also allows for targeted funding decisions.

Using registry data to evaluate the 2004 pneumococcal conjugate vaccine shortage.

BACKGROUND: The most recent pneumococcal conjugate vaccine (PCV7) shortage occurred between December 2003 and September 2004. To ensure vaccination of the highest-risk children, the Centers for Disease Control and Prevention recommended that providers delay administration of the third and fourth doses of vaccine to healthy children. We used Michigan Child Immunization Registry (MCIR) data collected from September 1, 2001 to November 30, 2004 to evaluate changes in PCV7 coverage. METHODS: Vaccination and demographic data from MCIR were reviewed for 420,733 children born between September 2001 and August 2004. Main outcome measures were the proportion of children who received the third dose of PCV7 by 7 months of age and the fourth dose of PCV7 by 16 months of age. Vaccine coverage for measles, mumps, and rubella vaccine (MMR) and diphtheria, tetanus, and acellular pertussis vaccine (DTaP) was used for comparison, as these vaccines were abundant during this time period and their administration schedule is the same as the third and fourth doses of PCV7, respectively. Data analysis was conducted in spring 2005. RESULTS: Coverage for the third dose of DTaP and the first dose of MMR remained steady, while PCV7 coverage for the third dose dropped from 29% to 11%, and the fourth dose dropped from 27% to 22% in the month following the recommendations to defer doses. Coverage returned close to pre-shortage levels shortly after the recommendations to resume the normal schedule. PCV7 coverage trends were similar for children seen in the private or public sector. CONCLUSIONS: Registry data can be useful for evaluating vaccination coverage trends during a shortage. Our findings suggest that providers were compliant with recommendations to alter vaccine administration during the shortage.

Evaluation of risk factors for rural infestation by Triatoma pallidipennis (Hemiptera: Triatominae), a Mexican vector of Chagas disease.

Control of Chagas disease requires control of its triatomine vectors, which requires an understanding of the determinants of infestation. Twenty-seven household environmental characteristics in the town of Chalcatzingo, Morelos, were analyzed for association with infestation by Triatoma pallidipennis, the predominant local vector. Data were obtained through timed household searches for triatomines and surveys that characterized intradomicile and peridomicile environments. Of the households surveyed, 28.4% were infested by T. pallidipennis. Cross-sectional multivariate logistic regression analyses were performed that regressed infestation on environmental variables. Of the 530 households in the town, 84% had sufficient data to be included. Adobe walls, agricultural products, junk piles, lack of bednets, and number of rabbits were significantly associated with intradomiciliary infestation. Junk piles and numbers of dogs, cats, and rabbits were significantly associated with peridomiciliary infestation. Junk piles, agricultural products, and numbers of cats, rabbits, and birds were significantly associated with overall infestation. Unexpectedly, presence of stone piles was not associated with infestation. The results of this study provide information for designing Chagas disease control programs in rural Mexican areas infested by T. pallidipennis.