Issue link: https://hi.iaq.net/i/191637
Climate Change, the Indoor Environment, and Health 158 CLIMATE CHANGE, THE INDOOR ENVIRONMENT, AND HEALTH fants each year. In the US elderly population, it accounts for an estimated 177,000 hospitalizations and 14,000 deaths (CDC, 2010). RSV appears to contribute to invasive pneumococcal disease more than influenza viruses do (Murdoch and Jennings, 2009; Talbot et al., 2005; Watson et al., 2006). Like influenza virus activity, RSV activity is highest in temperate climates during fall and winter months and into spring. However, there can be variability in the time of onset and duration, at least in more subtropical regions (CDC, 2010a). Unlike influenza virus, RSV is stabilized by higher humidity, and transmission in some studies correlates with relative humidity, lower temperature, and increased cloud cover (Meerhoff et al., 2009). Whether the mechanisms of these factors are due to direct effects on the virus or to indirect effects in driving people indoors into crowded environments is an open question. In some settings, such as Indonesia, RSV activity correlated strongly with rainfall and temperature (Omer et al., 2008). However, the apparently differing epidemiology in temperate and tropical climates remains incompletely explained (Welliver, 2009). In Spain, RSV admissions of infants with severe disease were strongly associated with lower temperature and lower absolute humidity (Lapeña et al., 2005). Rhinovirus Human rhinovirus (HRV) is a common and relatively mild pathogen, but one that by its very ubiquity and frequency has a major impact on human health, especially in the setting of pre-existing airway disease like asthma. Adults may have up to four bouts per year, typically in the fall through spring, accounting for up to 62 million cases in the United States annually (Sloan et al., 2011). In addition, because HRV is highly transmissible, settings that favor human-to-human and fomite transmission tend to result in relatively high rates of HRV during certain times of the year. Less research has been conducted on HRV than on influenza and RSV, in part because these latter organisms' morbidity and mortality are much higher and their etiologies somewhat less complex. Human rhinoviruses are comprised of three main groups—A, B, and C—which replicate in the epithelial cells of the upper and lower respiratory tracts, leading to cough, wheeze, and rhinorrhea (Dulek and Peebles, 2011). Allergic triggers act along with HRV to fuel the exacerbation of asthma. Extensive work has shown that HRV is one of the most prevalent cofactors in asthma exacerbations, making their role in overall medical care critical to understand and interrupt. A few studies address the determinants of HRV transmission and prevalence in indoor environments. Myatt et al. (2004) showed that the amount of HRV recovered from building air handling filters varied with the amount of outside air entrained, suggesting that HRV transmission might be influ- Copyright © National Academy of Sciences. All rights reserved.