Abstract
BackgroundIdentification of high-risk populations for serious infection due to S. pneumoniae will permit appropriately targeted prevention programs.MethodsWe conducted prospective, population-based surveillance for invasive pneumococcal disease and laboratory confirmed pneumococcal pneumonia in homeless adults in Toronto, a Canadian city with a total population of 2.5 M, from January 1, 2002 to December 31, 2006.ResultsWe identified 69 cases of invasive pneumococcal disease and 27 cases of laboratory confirmed pneumococcal pneumonia in an estimated population of 5050 homeless adults. The incidence of invasive pneumococcal disease in homeless adults was 273 infections per 100,000 persons per year, compared to 9 per 100,000 persons per year in the general adult population. Homeless persons with invasive pneumococcal disease were younger than other adults (median age 46 years vs 67 years, P<.001), and more likely than other adults to be smokers (95% vs. 31%, P<.001), to abuse alcohol (62% vs 15%, P<.001), and to use intravenous drugs (42% vs 4%, P<.001). Relative to age matched controls, they were more likely to have underlying lung disease (12/69, 17% vs 17/272, 6%, P = .006), but not more likely to be HIV infected (17/69, 25% vs 58/282, 21%, P = .73). The proportion of patients with recurrent disease was five fold higher for homeless than other adults (7/58, 12% vs. 24/943, 2.5%, P<.001). In homeless adults, 28 (32%) of pneumococcal isolates were of serotypes included in the 7-valent conjugate vaccine, 42 (48%) of serotypes included in the 13-valent conjugate vaccine, and 72 (83%) of serotypes included in the 23-valent polysaccharide vaccine. Although no outbreaks of disease were identified in shelters, there was evidence of clustering of serotypes suggestive of transmission of pathogenic strains within the homeless population.ConclusionsHomeless persons are at high risk of serious pneumococcal infection. Vaccination, physical structure changes or other program to reduce transmission in shelters, harm reduction programs to reduce rates of smoking, alcohol abuse and infection with bloodborne pathogens, and improved treatment programs for HIV infection may all be effective in reducing the risk.
Highlights
Streptococcus pneumoniae is the most common cause of bacterial pneumonia, bacteremia and meningitis in adults, and is a major cause of morbidity and mortality in the general population [1,2]
Homeless adults may be at greater risk than other adults both because of underlying medical conditions that increase their risk of infection such as chronic liver disease or HIV infection [2,3,4,5,6,7,8], and because communal living in shelters may be associated with transmission of pathogenic strains [8,9,10,11]
Two comparisons of risk factors for invasive pneumococcal disease were conducted: one in which risk factors in cases occurring homeless adults were compared to all cases in other adults, and one in which cases in homeless adults were compared a cohort of other adults constructed by identifying, for each case in a homeless person, the four cases of disease in housed persons closest in age
Summary
Streptococcus pneumoniae is the most common cause of bacterial pneumonia, bacteremia and meningitis in adults, and is a major cause of morbidity and mortality in the general population [1,2]. Authors of at least two reports of clusters of pneumococcal disease in shelters have recommended systematic vaccination of shelter residents [9,10]. No national guidelines currently include such a recommendation, and there are few data addressing the burden of illness associated with pneumococcal infection in the homeless. The objective of this study was to describe the epidemiology of serious pneumococcal disease in homeless adults in metropolitan Toronto over a five year period. Identification of high-risk populations for serious infection due to S. pneumoniae will permit appropriately targeted prevention programs
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