Community Acquired Infections Division, Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, 100 Eglantine Driveway, Ottawa, ON K1A 0K9, Canada. firstname.lastname@example.org
Investigations related to tuberculosis (TB) cases on airline flights have received increased attention in recent years. In Canada, reports of air travel by individuals with active TB are sent to the Public Health Agency of Canada (PHAC) for public health risk assessment and contact follow-up. A descriptive analysis was conducted to examine reporting patterns over time.
Reports of air travel by individuals with active TB received by PHAC between January 2006 and December 2008 were reviewed. Descriptive analyses were performed on variables related to reporting patterns, characteristics and actions taken.
The number of reports increased each year with 18, 35 and 51 reports received in 2006, 2007 and 2008, respectively. Of the 104 total cases, most were male (63%) and born outside of Canada (87%). Ninety-eight cases (97%) met the criteria for infectiousness and a contact investigation was initiated for 136 flights.
Reports of air travel by individuals with active TB have been increasing annually in Canada in recent years. Outcomes of the subsequent contact investigations, including passenger follow-up results and evidence of TB transmission, is necessary to further evaluate the effectiveness of the Canadian guidelines.
Accurate and precise estimates of the incubation distribution of novel, emerging infectious diseases are vital to inform public health policy and to parameterize mathematical models.
We discuss and compare different methods of estimating the incubation distribution allowing for interval censoring of exposures, using data from the severe acute respiratory syndrome (SARS) epidemic in 2003 as an example.
Combining data on unselected samples of 149 and 168 patients with defined exposure intervals from Toronto and Hong Kong, respectively, we estimated the mean and variance of the incubation period to be 5.1 day and 18.3 days and the 95th percentile to be 12.9 days. We conducted multiple linear regression on the log incubation times and found that incubation was significantly longer in Toronto than in Hong Kong and in older compared with younger patients, while it was significantly shorter in healthcare workers than in other patients.
Our findings suggest subtle but important heterogeneities in the incubation period of SARS among different strata of patients. Robust estimation of the incubation period should be independently carried out in different settings and subgroups for novel human pathogens using valid statistical methods.
Sexually Transmitted Diseases (STD) are a major health problem all over the world. The diseases are often spread by unsuspecting asymptomatic individuals. One important means of controlling STD is thus the identification of asymptomatic persons. The purposes of this thesis were a) to describe methods of identifying infected individuals through contact tracing and screening, b) to evaluate contact tracing routines, c) to compare epidemiological characteristics of two different groups of chlamydia-infected women and their partners and d) to see if data from contact tracing could be used in a model describing partner choice and STD spread. A microepidemic of penicillinase-producing gonococci was effectively controlled through contact tracing by cooperating counsellors. Serotyping of gonococci and graphic description proved of great help in mapping the contact chain. Contact tracing integrated in the psychosocial long-term care of HIV-infected patients resulted in identification of a great number of previously unidentified individuals. Screening for Chlamydia trachomatis (Ct) among asymptomatic patients of family planning clinics revealed a 7.3% Ct prevalence. Four factors were significantly correlated to the risk of being infected: age 18-23, duration of present relationship less than 1 year, failure to use condoms and no previous history of genital infection. Abstention from testing was especially high in areas with low socio-economic status. In these areas, increased resources for health care are needed. Five different levels of management of Ct infections were compared. Increased measures to verify that reported partners were examined decreased reinfections and after Ct was included in the STD Act more reported partners than before came for examination. Index patients found by chlamydia screening and their partners have a lower average number of recent partners than index patients visiting an STD clinic and their partners. Partners of female patients in the STD clinic group were also more often Ct-positive. The differences between the groups are small and do not justify different ambitions in partner management. Choice of steady partner was rather restricted and choice of casual partner followed a more random pattern. Our data thus do not support a pure random mixing model for STD spread.
BACKGROUND: Sexually transmitted infections are leading causes of morbidity for Canadian Aboriginal women. To date, very few initiatives have been successful in screening, treating, and limiting these infections among these populations. OBJECTIVES: To evaluate the efficacy of universal screening, treatment and contact tracing as a means of capturing a more accurate count of chlamydia and gonorrhea prevalence and limiting transmission among Inuit communities. METHODS: 181 participants were screened for chlamydia and gonorrhea and interviewed in a cross-sectional survey (Aug-Sept/03). Information was collected on demographics, use of health services, sexual histories and STI knowledge among others. A random sample (n = 100) from the cross-sectional group was selected for the longitudinal cohort. Individuals were followed every two months post baseline for four visits (Oct/03-May/04). At each visit, participants were screened for chlamydia/gonorrhea. All positive cases and their partners were treated and contact tracing completed. Logistic Regression analysis and the McNemar Test of Correlated Proportions were used to analyze the data. RESULTS: Overall, 35 cases of chlamydia were detected, with 21 detected at baseline and 14 during follow-up. The baseline prevalence was 11.6% in comparison with 2.7% that was previously estimated. No gonorrhea was detected. The strongest factor associated with a positive chlamydia was having recent STI (OR 9.82, CI: 2.70, 35.77). CONCLUSIONS: Consistent with the literature, the results support the use of universal screening followed by prompt treatment and contact tracing in populations with greater than 10% chlamydia prevalence.
BACKGROUND: Staphylococcus aureus is a frequent cause of serious infections. Methicillin-resistant S. aureus (MRSA) are resistant to almost all types of beta-lactam antibiotics and therefore represent a substantial medical problem. MATERIAL AND METHOD: In April 2006, the Department of Obstetrics at the Asker and Baerum hospital had an outbreak of MRSA that affected four newborns. The source for the infection was sought among family members, other patients and employees, and eradication was attempted. RESULTS: An employee was identified as the probable infectious source. Subsequent investigation identified 13 individuals infected by the same MRSA clone, which was Panton-Valentine-leukocidin (PVL) positive and therefore clearly a pathogen. 10 of the patients had MRSA disease, with 21 months between the first and the last identified case. For 5 of 13 patients MRSA was still detectable after the first attempt of eradication. For 2 patients, including one of the newborns, eradication has so far been unsuccessful and a third patient has acquired a new abscess after one year. INTERPRETATION: Issues connected to MRSA-screening of close contacts and eradication are resource-demanding and require careful consideration of strategy, especially for small children and families with chronic MRSA carriers. Updated detailed national guidelines for MRSA management are needed.
To define a population-level cohort of individuals infected with the human immunodeficiency virus (HIV) in the province of British Columbia from available registries and administrative datasets using a validated case-finding algorithm.
Individuals were identified for possible cohort inclusion from the BC Centre for Excellence in HIV/AIDS (CfE) drug treatment program (antiretroviral therapy) and laboratory testing datasets (plasma viral load (pVL) and CD4 diagnostic test results), the BC Centre for Disease Control (CDC) provincial HIV surveillance database (positive HIV tests), as well as databases held by the BC Ministry of Health (MoH); the Discharge Abstract Database (hospitalizations), the Medical Services Plan (physician billing) and PharmaNet databases (additional HIV-related medications). A validated case-finding algorithm was applied to distinguish true HIV cases from those likely to have been misclassified. The sensitivity of the algorithms was assessed as the proportion of confirmed cases (those with records in the CfE, CDC and MoH databases) positively identified by each algorithm. A priori hypotheses were generated and tested to verify excluded cases.
A total of 25,673 individuals were identified as having at least one HIV-related health record. Among 9,454 unconfirmed cases, the selected case-finding algorithm identified 849 individuals believed to be HIV-positive. The sensitivity of this algorithm among confirmed cases was 88%. Those excluded from the cohort were more likely to be female (44.4% vs. 22.5%; p
Since 1989 the reporting of chlamydia infections is regulated by the Contagious Diseases Act, which stipulates that a physician who detects chlamydia is obliged to trace the patient's sexual partner(s). Up to 1994 the annual decrease in the number of chlamydia cases was 20 percent, which did not meet the goal stipulated by the County Council. A questionnaire study was carried out concerning diagnosis, treatment and public health intervention in chlamydia patients seen by general and private practitioners. While the clinical management was seen to adhere to the recommendations of the National Board of Health, adequate tracing of sexual contacts was not carried out in 20-45 per cent of the cases. In a major urban area, such as the County of Stockholm, referral of all chlamydia cases to specialist clinics could possibly improve not only the care of the patients but also the success rate in reaching their sex partners.