Human adenoviruses (HAdVs) frequently infect children, mainly causing diseases of the respiratory, ocular, and gastrointestinal tracts. Although most HAdV acute respiratory illnesses (ARIs) are mild and self-limited, severe and occasionally fatal infections have been reported in newborns and infants (1
), the immunodeficient (2
), those with underlying comorbidities (3
), and occasionally, otherwise healthy adults (4
HAdVs are classified within the family Adenoviridae
, genus Mastadenovirus
, and are further divided into seven species (A to G) and over 50 recognized types (8
). Clinical symptoms, disease severity, and epidemiological patterns of infection are often determined by virus species or type. HAdV ARI is most often caused by species B, C, and E viruses. Species C viruses are ubiquitous and endemic in pediatric populations, where infections are often subclinical or lead to sporadic ARIs (9
). Species B (primarily types 3, 7, 11, 14, and 21) and the sole species E (type 4) viruses have been associated with epidemics of often severe ARIs affecting children and adults. Community HAdV ARI clusters, as recently occurred with the emergence of HAdV strain 14p1 in the United States and Europe (10
), including discrete institutional outbreaks among civilians (13
), outbreaks covering wide geographic areas (6
), and continuous outbreaks among unvaccinated military personnel undergoing basic training (17
), have been reported.
Laboratory diagnosis of HAdV infection can be achieved by virus isolation, antigen detection, PCR, and serology. Serotype identification is classically performed by serum neutralization and/or hemagglutination inhibition with type-specific hyperimmune animal antisera. Immunotyping methods provide definitive identification of serotype but are excessively time-consuming, labor-intensive, and restricted to a few laboratories that possess reference immune reagents. A variety of molecular methods have been advanced to augment immunotyping, including genome restriction analysis (20
), PCR-coupled microarrays (21
), PCR-fragment length analysis (23
), electrospray ionization mass spectrometry (24
), and more commonly, partial sequencing of specific target genes (25
). Although an advance over immunotyping methods, these methods require specialized technical skills and utilize technologies that may be of limited availability outside the research laboratory setting.
Single and multiplex conventional and real-time quantitative PCR (qPCR) assays using species- and type-specific primers/probes have been described for some HAdVs that cause ARIs (27
). qPCR is particularly well suited for this purpose, offering (i) a closed system with a low risk from amplicon contamination, (ii) rapid, quantitative, and high-throughput specimen testing, (iii) a wide network of technical expertise and available instrumentation, and (iv) easy implementation and integration into existing qPCR assay panels for other respiratory pathogens. For these reasons, we developed and validated sensitive and type-specific qPCR assays for detection and identification of the epidemic-associated respiratory HAdVs, types 3, 4, 7, 11, 14, 16, and 21, to facilitate rapid outbreak response.
(Data from this study were presented at the 27th Clinical Virology Symposium, Daytona, FL, 8 to 11 May 2011.)