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2013-2014 human adenovirus outbreak suggests re-emergence in US
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Recent data published in Emerging Infectious Diseases implicated multiple human adenoviruses in a 2013-2014 outbreak affecting nearly 200 people.
These cases were primarily associated with the relatively uncommon human adenovirus (HAdV)-B7 and could represent a potential re-emergence of the disease in the United States, according to Magdalena Kendall Scott, MPH, epidemiologist for the Oregon Public Health Division (OPHD), and colleagues.
“Circulating HAdVs can vary temporally and geographically; emergent genomic variants are possibly associated with more severe illness,” they wrote. “Recent reports have noted severe respiratory disease associated with the re-emergence of HAdV-B7 and genomic variant 7d in China and other countries in Asia. However, HAdV-B7 was rarely reported in the United States during the past decade.”
Upon reports of increased HAdV detection during March 2014, OPHD instructed three hospital systems comprising 14 health care facilities to report all HAdV-positive specimens collected from respiratory infection patients diagnosed after September 2013. Along with reviewing patient medical records and historical HAdV detection data, OPHD submitted all available clinical specimens to CDC for HAdV confirmation and molecular typing.
Scott and colleagues noted an 11-fold increase in Oregon HAdV detections reported to the National Respiratory and Enteric Virus Surveillance System from November 2013 to April 2014. They identified 198 patients with a HAdV-positive respiratory specimen from Oct. 9, 2013 to July 7, 2014, 56% of which were reported from hospital systems in or surrounding Portland. Ninety-one percent of the cases were Oregonians.
Of the 109 positive specimens available for typing, 59% were HAdV-B7, 13% were HAdV-C2, 9% were HAdV-B21, and 9% were HAdV-C1. Genomic data from seven HAdV-B7 samples found the viruses to be nearly identical to those circulating in China in 2009 and 2011, and cases with HAdV-B7 were significantly older than those with other HAdV types.
Thirty-two percent of patients experienced pneumonia, 69% were hospitalized and 2.5% died. HAdV-B7 patients were more often hospitalized, admitted to an ICU, mechanically ventilated and required longer stays.
The researchers hypothesized that the worsened outcomes among HAdV-B7 patients could be the result of enhanced virus fitness or low herd immunity. Because shifts in HAdV type may be associated with severe disease and community outbreaks, they urged health care providers to consider HAdV when diagnosing patients with pneumonia or acute respiratory infection and participate in HAdV surveillance.
“HAdV-B7 might be re-emerging in the United States and might be associated with increased numbers of severe respiratory infections,” Scott and colleagues wrote. “Tracking the emergence of HAdV types in the United States will lead to early identification of new types and potential variants of known types.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
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