New Respiratory Viruses and the Elderly

Jartti, Laura; Langen, Henriikka; Söderlund-Venermo, Maria; Vuorinen, Tytti; Ruuskanen, Olli; Jartti, Tuomas

Of the conventional diagnostic methods available for these new respiratory viruses, serology is available for the influenza virus, MPV, HBoV and PyVs [62, 73, 109, 132, 133] . However, serology is not often practical in the acute phase. Of the other conventional methods, a rapid antigen detection test is available for the influenza virus. Some reports suggest that a rapid antigen detection test is relatively sensitive for detection of the influenza virus in elderly patients; during outbreaks up to 77% are detected by rapid antigen testing of culture positive samples [133, 134] . Other studies have reported much lower sensitivities (38-43% compared with PCR) [135, 136] . The sensitivity may be only 8-22% in patients ! 80 years of age [137] . Despite a poor sensitivity, the rapid antigen detection test is highly specific for detecting influenza viruses in the elderly All new respiratory viruses can be diagnosed by sensitive PCR methods [44] . When diagnosing acute HBoV or SARS-CoV infection, PCR needs to be complemented with serology. Currently, up to 85-95% of all viruses in respiratory samples of children with respiratory symptoms may be detected [61, [138] [139] [140] [141] [142] . PCR is the best choice also for the elderly since it is the most sensitive method for detection of viruses in this age group as well [136, [143] [144] [145] [146] [147] , although the detection rates, probably due to the difficulties in sampling, decline with age. The detection rates among elderly patients have remained below 40% even in exacerbations of chronic pulmonary disease [91, 92, 95, 148] and viral pneumonia [149] . The rates in the intermediate age groups, i.e., adults with exacerbations of COPD or asthma have been up to 64% [150] [151] [152] . The actual prevalences of the new viruses among the elderly population are not known [5, 7, 10, 11, 148, 153] .