Assessing secondary attack rates among household contacts at the beginning of the influenza A (H1N1) pandemic in Ontario, Canada, April-June 2009: a prospective, observational study.

BACKGROUND: Understanding transmission dynamics of the pandemic influenza A (H1N1) virus in various exposure settings and determining whether transmissibility differed from seasonal influenza viruses was a priority for decision making on mitigation strategies at the beginning of the pandemic. The objective of this study was to estimate household secondary attack rates for pandemic influenza in a susceptible population where control measures had yet to be implemented. METHODS: All Ontario local health units were invited to participate; seven health units volunteered. For all laboratory-confirmed cases reported between April 24 and June 18, 2009, participating health units performed contact tracing to detect secondary cases among household contacts. In total, 87 cases and 266 household contacts were included in this study. Secondary cases were defined as any household member with new onset of acute respiratory illness (fever or two or more respiratory symptoms) or influenza-like illness (fever plus one additional respiratory symptom). Attack rates were estimated using both case definitions. RESULTS: Secondary attack rates were estimated at 10.3% (95% CI 6.8-14.7) for secondary cases with influenza-like illness and 20.2% (95% CI 15.4-25.6) for secondary cases with acute respiratory illness. For both case definitions, attack rates were significantly higher in children under 16 years than adults (25.4% and 42.4% compared to 7.6% and 17.2%). The median time between symptom onset in the primary case and the secondary case was estimated at 3.0 days. CONCLUSIONS: Secondary attack rates for pandemic influenza A (H1N1) were comparable to seasonal influenza estimates suggesting similarities in transmission. High secondary attack rates in children provide additional support for increased susceptibility to infection.

Public perceptions of drinking water: a postal survey of residents with private water supplies.

BACKGROUND: In Canada, the legal responsibility for the condition of private water supplies, including private wells and cisterns, rests with their owners. However, there are reports that Canadians test these water supplies intermittently and that treatment of such water is uncommon. An estimated 45% of all waterborne outbreaks in Canada involve non-municipal systems. An understanding of the perceptions and needs of Canadians served by private water supplies is essential, as it would enable public health professionals to better target public education and drinking water policy. The purpose of this study was to investigate the public perceptions of private water supplies in the City of Hamilton, Ontario (Canada), with the intent of informing public education and outreach strategies within the population. METHODS: A cross-sectional postal survey of 246 residences with private water supplies was conducted in May 2004. Questions pertained to the perceptions of water quality and alternative water sources, water testing behaviours and the self-identified need for further information. RESULTS: Private wells, cisterns or both, were the source of household water for 71%, 16% and 13% of respondents, respectively. Although respondents rated their water quality highly, 80% also had concerns with its safety. The most common concerns pertained to bacterial and chemical contamination of their water supply and its potential negative effect on health. Approximately 56% and 61% of respondents used in-home treatment devices and bottled water within their homes, respectively, mainly due to perceived improvements in the safety and aesthetic qualities compared to regular tap water. Testing of private water supplies was performed infrequently: 8% of respondents tested at a frequency that meets current provincial guidelines. Two-thirds of respondents wanted more information on various topics related to private water supplies. Flyers and newspapers were the two media reported most likely to be used. CONCLUSION: Although respondents rated their water quality highly, the majority had concerns regarding the water from their private supply, and the use of bottled water and water treatment devices was extensive. The results of this study suggest important lines of inquiry and provide support and input for public education programs, particularly those related to private water testing, in this population.

Cerebrospinal fluid concentrations of vincristine after bolus intravenous dosing: a surrogate marker of brain penetration.

BACKGROUND: Vincristine (VCR) is used widely in oncology practice, and regular dosing is commonly associated with the development of sensorimotor or autonomic neuropathies. However, the incidence of VCR-related central nervous system (CNS) toxicity is comparatively low, suggesting that the blood-brain barrier may limit drug penetration into the brain parenchyma. This study determined whether measurable concentrations of VCR could be detected in the cerebrospinal fluid (CSF), as a surrogate marker of brain parenchyma penetration, after bolus intravenous injection in children without primary CNS pathology. METHODS: The authors studied 17 pediatric patients ages 2.5-14.1 years (median, 6.8 years) with acute lymphoblastic leukemia or non-Hodgkin lymphoma without evidence of leptomeningeal disease. Patients received VCR 1.5 mg/m2 by intravenous bolus injection followed at varying intervals by lumbar puncture for scheduled intrathecal methotrexate administration under general anesthesia. Paired VCR concentrations in both plasma and CSF were measured in each patient simultaneously at times ranging from 8 minutes to 146 minutes after the VCR injection. Three patients were studied twice. The paired samples were stored at -40 degrees C until analysis using a high performance liquid chromatography assay with a sensitivity of 0.1 microg/L in CSF and 0.4 microg/L in plasma. RESULTS: Plasma VCR concentrations ranged from 2.2 microg/L to 91.2 microg/L. No measurable VCR concentrations were detected in the CSF samples. CONCLUSIONS: Measurable concentrations of VCR in CSF are not achieved after the administration of standard intravenous bolus doses of VCR. The current observations are consistent with the relative rarity of VCR-related CNS neurotoxicity compared with the commonly observed sensorimotor and autonomic neuropathies. These findings suggest that the penetration of VCR into the brain parenchyma of patients with a relatively intact blood-brain barrier is low and that VCR may have a limited role in the CNS-directed therapy of these patients.