Deaths in the Elderly Associated with Several Common Viruses
By Amesh A. Adalja MD, FACP, July 27, 2012
Although mortality statistics often list “pneumonia and influenza” as a leading cause of death among the elderly, unbundling that category can reveal important pathogen-specific granularity, as demonstrated by a recently published study from the Netherlands.
Influenza A and RSV Universally Associated with Mortality
Van Asten and colleagues used weekly data collected on 9 pathogens—influenza A, influenza B, RSV, parainfluenza, rotavirus, norovirus, enterovirus, Camplyobacter, and Salmonella—from 3 national surveillance databases. They compared that data with statistics on weekly deaths occurring in the Netherlands. The researchers focused their analysis on people aged 65 years and older, stratified into 3 age cohorts: 65-74 years, 75-84 years, and 85 years and older. Regression analysis was used to assess the association between mortality and circulation levels of each of the 9 pathogens.
Overall, the association between levels of circulating pathogens and mortality was stronger among older subjects. Only influenza A virus and RSV were associated with mortality across all age cohorts. In subjects 75 years and older, influenza B and parainfluenza circulation coincided with mortality, and only norovirus was associated with mortality in people 85 years and older. Salmonella, Campylobacter, rotavirus, and enterovirus showed no mortality association.
The researchers found a time lag between pathogen circulation and deaths. For example, deaths typically lagged RSV circulation by 2-3 weeks; with parainfluenza, lag time varied across age groups.
RSV Overlooked as Cause of Morbidity and Mortality in the Elderly
The authors then attempted to estimate the fraction of mortality accounted for by specific pathogens. In those aged 85 years and older, 6.8% of mortality was estimated to be attributable to influenza A, influenza B, RSV, and parainfluenza. Overall, influenza A and RSV were associated with the highest proportion of deaths. Surprisingly, RSV accounted for nearly the same proportion of deaths in the elderly as influenza A.
The revelation of RSV as a cause of death in the elderly is an important finding. RSV is a common source of infection in infants and children, and a monoclonal antibody is available for prophylaxis of high risk premature infants. However, adults are not often tested or treated for RSV (inhaled ribavirin is available but seldom used for myriad reasons). Given the new study results indicating that RSV accounts for the same burden of mortality, this pathogen should be considered on par with influenza A in certain respects. For example, identification of influenza in a hospitalized patient leads to initiation of infection control measures to minimize risk of nosocomial spread. RSV is spread by the same mechanisms as influenza. Therefore, a case of RSV in a healthcare setting warrants the same infection control actions. However, because they are not often tested for, RSV infections, which may present as community acquired pneumonia or COPD exacerbations, are unknowingly admitted to hospitals without infection control measures in place. A second implication of the association of RSV with mortality is that it should provide impetus to pharmaceutical companies to develop new antivirals to treat RSV infection.
Van Asten L, van den Winjgaard C, van Pelt W, et al. Mortality attributable to 9 common infections: significant effect of influenza A, respiratory syncytial virus, influenza B, norovirus, and parinfluenza in elderly persons. J Infect Dis 2012; doi:10.1093/jinfdis/jis415.