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Please cite this paper as: Janjua et al. (2012) Transmission dynamics and risk factors for pandemic H1N1-related illness: outbreak investigation in a rural community of British Columbia, Canada. Influenza and Other Respiratory Viruses 6(3), e54-e62. Objective To characterize the first-wave epidemiologic features of influenza-like illness (ILI) associated with the novel pandemic A/H1N1 [A(H1N1)pdm09] virus. Methods We used generalized linear mixed models (GLMM) to assess risk factors and non-parametric and/or parametric distributions to estimate attack rates, secondary attack rates (SAR), duration of illness, and serial interval during a laboratory-confirmed community outbreak of A(H1N1)pdm09 clustered around on-reserve residents and households of an elementary school in rural British Columbia, Canada, in late April/early May 2009. ILI details were collected as part of outbreak investigation by community telephone survey in early June 2009. Results Overall, 92/408 (23%) of participants developed ILI and 36/408 (9%) experienced medically attended ILI (MAILI). The overall SAR in households was 22%: highest among participants 1-4 years of age (yoa) (50%) followed by <1 yoa (38%), 5-8 yoa (20%), 10-19 yoa (13%), 20-49 yoa (20%), and 50-64 yoa (0%). The median serial interval was estimated at 3·5 days (95% CI: 2·1-5·1). In multivariable GLMM analysis, having a chronic condition (OR: 2·58; 95% CI: 1·1-6·04), younger age [1-8 yoa: OR: 4·63; 95% CI: 2·25-9·52; 9-19 yoa: OR: 1·95; 95% CI: 0·97-3·9 (referent: ≥20 yoa)] and receipt of 2008-2009 influenza vaccine (OR: 2·68; 95% CI: 1·37-5·25) were associated with increased risk of ILI. Median duration of illness was 9 days, longer among those with chronic conditions (21 days). Median time to seeking care after developing illness was 4·5 days. On-reserve participants had higher chronic conditions, household density, ILI, MAILI, and SAR. Conclusions During a community outbreak of A(H1N1)pdm09-related illness, we identified substantial clinical ILI attack rates exceeding 20% with secondary household attack rates as high as 50% in young children. The serial interval was short suggesting a narrow period to prevent transmission. [ABSTRACT FROM AUTHOR]

An association between leukoencephalopathy, a disease of the white matter of the brain, and smoking heroin is well recognized. This paper describes 27 cases of leukoencephalopathy identified in two cities in British Columbia, Canada 2001-2006; the largest number of geographically and temporally defined reported cases in North America. Twenty cases of leukoencephalopathy were identified in and around Vancouver with onset dates December 2001 to July 2003; seven further cases were identified in Victoria September 2005-August 2006. Twenty (74%) of all cases were male, two couples were reported and eleven cases (55%) had Asian ethnicity. One case reported smoking heroin on a single occasion and developed mild symptoms; all other cases were hospitalized. Thirteen (48%) cases died; all had smoked heroin for a minimum of 3 years. Testing of one available heroin sample identified no substance other than common cutting agents. Although a specific etiology was not identified our study supports the theory of an intermittent exposure to a toxic agent added to the heroin or a combustion by-product. It also suggests a dose response effect rather than genetic predisposition. Collaboration with public health, health professionals, law enforcement and persons who use illegal drugs, will facilitate the early identification of cases to enable timely and complete follow-up including obtaining samples. Testing of implicated heroin samples may allow identification of the contaminant and therefore prevent further cases. It is therefore important to ensure key stakeholders are aware of our findings. [ABSTRACT FROM AUTHOR]

Background. In April 2009, an elementary school outbreak of pandemic H1N1 (pH1N1) influenza was reported in a community in northern British Columbia, Canada—an area that includes both non-Aboriginal and Aboriginal residents living on or off a reserve. During the outbreak investigation, we explored the relationship between prior receipt of trivalent inactivated influenza vaccine (TIV) and pH1N1-related illness. Methods. A telephone survey was conducted from 15 May through 5 June 2009 among households of children attending any school in the affected community. Members of participating households where influenza-like illness (ILI) was described were then invited to submit blood samples for confirmation of pH1N1 infection by hemagglutination inhibition and microneutralization assays. Circulation of pH1N1 was concentrated among households of the elementary school and elsewhere on-reserve to which analyses of TIV effect were thus restricted. Odds ratios (ORs) for the TIV effect on ILI were computed through logistic regression, with adjustment for age, comorbidity, household density, and Aboriginal status. The influence of within-household clustering was assessed through generalized-linear-mixed models. Results. Of 408 participants, 92 (23%) met ILI criteria: 29 (32%) of 92 persons with ILI, compared with 61 (19%) 316 persons without ILI, had received the 2008-2009 formulation of TIV. Fully adjusted ORs for 2008- 2009 TIV effect on ILI were 2.45 (95% confidence interval, 1.34-4.48) by logistic regression and 2.68 [95% confidence interval, 1.37-5.25) by generalized-linear-mixed model. Conclusions. An outbreak investigation in British Columbia during the late spring of 2009 provided the first indication of an unexpected association between receipt of TIV and pH1N1 illness. This led to 5 additional studies through the summer 2009 in Canada, each of which corroborated these initial findings. [ABSTRACT FROM AUTHOR]