Adenovirus Type 4 Respiratory Infections among Civilian Adults, Northeastern United States, 2011–2015

: Human adenovirus type 4 (HAdV-4) is most commonly isolated in military settings. We conducted detailed molecular characterization on 36 HAdV-4 isolates recovered from civilian adults with acute respiratory disease (ARD) in the northeastern United States during 2011-2015. Specimens came from college students, residents of long-term care facilities or nursing homes, a cancer patient, and young adults without co-morbidities. HAdV-4 genome types 4a1 and 4a2, the variants most frequently detected among US military recruits in basic training before the restoration of vaccination protocols, were isolated in most cases. Two novel a-like variants were recovered from students enrolled at a college in Tompkins County, New York, USA, and a prototype-like variant distinguishable from the vaccine strain was isolated from an 18-year-old woman visiting a physician's office in Ulster County, New York, USA, with symptoms of influenza-like illness. Our data suggest that HAdV-4 might be an underestimated causative agent of ARD among civilian adults.

To the Editor: We read with interest the article by Kajon et al. (1), which highlighted that human adenovirus type 4 might be an underrecognized cause of acute respiratory disease (ARD) outside military settings. We report that human adenovirus B7 (HAdV-B7) might also be a cause of this disease.
HAdV-B7 is well recognized as a causative agent of neonatal disease and infections in immunocompromised patients. However, we identified an unusual cluster of 4 cases of severe ARD caused by this pathogen in immunocompetent adults in Dublin, Ireland. These patients had acute respiratory illness when they came to the emergency department of Mater Misericordiae University Hospital in Dublin. The patients came to the hospital over a 4-week period during the summer of 2017, and each patient required intensive care support for single-organ failure. Three patients required intubation and ventilation; all 4 patients recovered.
Three patients reported gastrointestinal and respiratory symptoms, as seen in Oregon, USA (2). Although coinfection with other viruses or bacteria has been described (3), only 1 patient in our cluster had a possible concomitant pathogen. None of the 4 patients were given antiviral therapy but all received antimicrobial drugs.
All 4 case-patients were either homeless or in temporary accommodations for homeless adults, but we did not identify any epidemiologic link. The Department of Public Health and temporary accommodation sites were notified to raise awareness and offer early testing of symptomatic persons. However, no additional cases were identified.
HAdV-B7 was identified by BLAST analysis (https:// blast.ncbi.nlm.nih.gov/Blast.cgi) of viral hexon genes (4). Each virus had 100% identity within the region sequenced to a strain previously associated with respiratory illness in a military training camp in China (GenBank accession no. KP896481).
This cluster of HAdV-B7 causing severe ARD in immunocompetent adults appears to have no clear epidemiologic link. We agree that HAdV might be an underrecognized pathogen in severe communityonset ARD. Testing for viral respiratory pathogens should be considered in all patients and not just the immunocompromised. (2). The viruses from South Korea have PB2 and polymerase acidic genes distinct from those of viruses from the Netherlands. H5N6 subtype viruses were also detected in Greece, Japan, and Taiwan in 2017. Viruses from these regions have the same genotype, but PB2, polymerase acidic, and neuraminidase genes differ from those in the viruses from the Netherlands. Clade 2.3.4.4 group A H5N8 subtype viruses emerged in East Asia in early 2014 and subsequently spread, along migratory bird routes, to Europe and North America by the end of 2014. H5N8 subtype and reassortant viruses, including H5N1 and H5N2 subtypes (3), resulted in the deaths of 7.5 million turkeys and 42.1 million chickens in the United States alone. Since June 2016, these H5N8 subtype viruses have circulated in Europe and reassorted with local low pathogenicity avian influenza viruses. Group B H5N8 subtype viruses caused the long-lasting second wave of outbreaks in wild birds and poultry in 30 countries in Europe, including the Netherlands, Belgium, Luxembourg, and the United Kingdom (4). It is hard to predict whether novel clade 2.3.4.4 group B H5N6 subtype viruses might trigger a similar new wave of massive HPAI H5Nx outbreaks in wild and domestic birds and even cause infections among poultry workers. However, more surveillance data are needed to investigate the genetic diversity and evolution of these viruses and how widely they are circulating in wild birds.