The impact of adulticide applications on mosquito density in Chicago, 2005.

The city of Chicago used ground ultra-low volume treatments of sumithrin (ANVIL 10+10) in areas with high West Nile virus infection rates among Culex mosquitoes. Two sequential treatments in Morbidity and Mortality Weekly Reports wk 31 and 32 decreased mean mosquito density by 54% from 2.5 to 1.1 mosquitoes per trap-day, whereas mosquito density increased by 153% from 1.3 to 3.3 mosquitoes per trap-day at the nonsprayed sites. The difference between these changes in mosquito density was statistically significant (confidence intervals for the difference in change: -4.7 to -1.9). Sequential adulticide treatments in September (wk 34 and 35) had no effect on mosquito density, probably because it was late in the season and the mosquitoes were presumably entering diapause and less active. Overall, there was significant decrease in mosquito density at the trap sites treated in all 4 wk (wk 31, 32, 34, and 35), suggesting that sustained sequential treatments suppressed mosquito density. Maximum likelihood estimates (MLE) of infection rate estimates varied independently of adulticide treatments, suggesting that the adulticide treatments had no direct effect on MLE. Mosquito trap counts were low, which was probably due to large numbers of alternative oviposition sites, especially catch basins competing with the gravid traps.

Clinical characteristics and functional outcomes of West Nile Fever.

BACKGROUND: West Nile fever, considered a nonsevere manifestation of West Nile virus infection, has not been clinically well described in the United States. In 2002, Illinois had 884 documented cases of West Nile virus infection with 66 associated deaths. OBJECTIVE: To describe the symptoms and functional outcomes of West Nile fever. DESIGN: Case series. SETTING: Illinois. PATIENTS: 98 community-dwelling patients with laboratory evidence of West Nile virus infection but no history of clinical evidence of meningitis, encephalitis, or acute flaccid paralysis. INTERVENTION: Outpatient interviews. MEASUREMENTS: Presence and duration of patient-reported symptoms of infection, symptom-associated absenteeism, health care use, and impact on daily activities. RESULTS: Of 98 patients, 96% had fatigue for a median of 36 days, 81% had fever for a median of 5 days, 71% had headache for a median of 10 days, 61% had muscle weakness for a median of 28 days, and 53% had difficulty concentrating for a median of 14 days. Thirty respondents reported hospitalization, with a median stay of 5 days. At 30 days after onset, 63% of respondents continued to have symptoms. Duration did not vary significantly with increased age. Among the 72 patients who normally attended work or school, 57 (79%) could not attend because of illness (median absence, 10 days). LIMITATIONS: Recall bias could have been introduced by the delay between illness onset and interview and by self-reporting of illness information. CONCLUSIONS: West Nile fever is a more severe illness than has previously been documented. Mandatory reporting of West Nile fever cases in addition to West Nile meningoencephalitis cases could allow more accurate and timely recognition of the geographic distribution of West Nile virus infections and could inform public health interventions.

Underimmunization in Chicago children who dropped out of WIC.

BACKGROUND: The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves a large proportion of Chicago infants, but some discontinue participation before age 1 year. To determine if children who remained active at WIC immunization-linked sites after their first birthday were more likely to be immunized by ages 19 and 25 months than those who dropped out, a retrospective cohort study was conducted. METHODS: Four Chicago WIC sites that used monthly voucher pick-up were chosen. Children born from July 1, 1997 to September 30, 1997 who attended these sites were eligible (N=1142). The cohort was divided into two groups: (1) active group (46%), who had a WIC visit on or after their first birthday; and (2) inactive group (54%), who had their last WIC visit before their first birthday. Children were enrolled through home visits. RESULTS: The records for 200 children were analyzed. By age 19 months, 65 (84%) of 77 active children had received one dose of measles-mumps-rubella vaccine (MMR), compared to 82 (67%) of 123 inactive children (risk ratio [RR]=1.3; 95% confidence interval [CI], 1.1- 1.5). By age 25 months, 64 (83%) active children had received four doses of diphtheria-tetanus-pertussis vaccine (DTP), one MMR, and three doses of Haemophilus influenzae type b vaccine (Hib), compared with 64 (52%) inactive children (RR=1.6; 95% CI, 1.3-2.0). CONCLUSIONS: In this cohort, children active in WIC after their first birthday were more likely to be immunized by ages 19 and 25 months, compared with those who were no longer active. Chicago children who drop out of WIC may represent those at highest risk for underimmunization and may require special strategies to improve coverage.

Intensive investigation of bacterial foodborne disease outbreaks: proposed guidelines and tools for the collection of dose-response data by local health departments.

Local health departments that investigate foodborne disease outbreaks do not have adequate guidelines for collecting data that could be used to estimate dose-response relationships, a key component of hazard characterization in quantitative microbial risk assessment. To meet this need, criteria and a questionnaire template for the collection of appropriate dose-response data in the context of outbreaks were developed and applied in the investigation of a point-source outbreak linked to Salmonella serotype Enteritidis in a salmon entrée in February 2000. In this outbreak, the attack rate and risk of hospitalization increased with the amount of salmon entrée consumed, and detailed data were obtained on illness severity measures and host susceptibility factors. Local health departments might consider broadening investigations to include the collection of additional data when investigating outbreaks that have met a specific set of conditions. These data could provide information needed by federal regulatory agencies and other organizations for quantitative microbial risk assessment. Intensive investigations of outbreaks could prevent future illnesses by providing information needed to develop approaches to minimizing risk.