National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine research support non-u.s. gov't female male aged middle aged 80 and over Incidence Antigens Viral / analysis pneumonia fluorescent antibody technique virus cultivation community-acquired infections / epidemiology* community-acquired infections / diagnosis viral / diagnosis virus diseases / diagnosis reverse transcriptase polymerase chain reaction virus diseases / virology viral / epidemiology* virus diseases / epidemiology viruses / genetics viral / virology* community-acquired infections / virology* nasopharynx / virology viruses / classification viruses / isolation & purification* antoni torres pmid:16759052 maria angeles marcos marta camps specimen handling / methods