Adenovirus Serotype 14 Fatal Colds Due to Recombinant?
Recombinomics Commentary
November 16, 2007
Adenovirus serotype 14 (Ad14) is a rarely reported but emerging serotype of adenovirus that can cause severe and sometimes fatal respiratory illness in patients of all ages, including healthy young adults.
Ad14 isolates from all four states were identical by sequence data from the full hexon and fiber genes. However, the isolates were distinct from the Ad14 reference strain from 1955, suggesting the emergence and spread of a new Ad14 variant in the United States.
The above comments in this week’s MMWR in the report entitled “Acute Respiratory Disease Associated with Adenovirus Serotype 14 – Four States 2006-2007” raise questions about the genetic changes in the Ad14 variant.
Most of the cases described in the report involve recruits at Lackland Air Force base in Texas where 106 recruits tested positive for Ad14 between February and June of this year. 27 were hospitalized and 5 of those patients were moved to the ICU where 1 died. The death of a young (19F) recruit from adenovirus is cause for concern.
A related report, described the appearance of Ad14 at multiple military bases in 2006. 10 of these cases are detailed by the San Diego site at the National Service for Emerging Adenovirus Infections website. The cases (at Fort Benning in Georgia, Great Lakes in Illinois, MCRD in San Diego) are listed at the site and are also referenced in a publication entitled, “Abrupt emergence of diverse species B1 and B2 adenovirus in US military recruit training centers” which describes the recent appearance of Ad14 at multiple military sites.
In addition, the MMWR report indicates infections at Lackland are continuing among recruits, as well as nurses treating the recruits, and recruits at other bases in Texas.
However, in addition to the spread of Ad14 at military sites, the MMWR describes infections in civilians in Oregon, Washington State, and New York. Most of these cases were in Oregon, where 31 cases were identified. Of these, 22 were hospitalized and 16 were transferred to the ICU where 7 died. At the other two sites, 2 of 5 patients died (one also had HIV and one was a newborn). Thus, 9 of the 36 patients infected with AD14 died, producing a case fatality rate of 25%. In Oregon, the median age of the fatal cases was 63.6 years.
The number of Ad14 cases in the general population is not clear. Although the 15 centers have been testing patients, the number of cases tested has been limited, and the serotypes detected at the centers have regional distributions, indicating the testing is far from comprehensive and pockets of Ad14 infections may be undiagnosed. The announcement in the MMWR should lead to the identification of more suspect cases.
The changes in the Ad14 sequence should be of interest. Adenovirus evolves via homologous recombination, and the report on the military sites noted the high frequency of dual or triple adenovirus infections, which are required for homologous recombination.
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