Adenovirus Serotype 14 Emergence
Recombinomics Commentary
November 17, 2007
In March and April of 2006, Ad14 (subspecies B2) simultaneously emerged at 5 training centers, including San Diego, Lackland, Fort Leonard Wood, Great Lakes, and Fort Benning, thereby affecting all services except the Coast Guard (Cape May). At 3 of these centers, Ad14 first appeared in coinfections with AdB1 serotypes and in 1 case as part of a triple infection with Ad4 and Ad7. Ad14 maintained a consistent presence at Fort Benning, San Diego, and Great Lakes during summer 2006. At the same time, a variety of AdB1 serotypes emerged at all sites except Cape May. Ad3 cases were clustered at Fort Jackson, Ad7 at Fort Leonard Wood and Parris Island, and Ad21 at Parris Island and Fort Benning. All 6 identified serotypes were seen at Fort Benning during one 2-month period. Many coinfections were identified, the majority of which were coinfections with Ad4 and one of the species B serotypes.
The above comments, from a recent paper entitled, “Abrupt Emergence of Diverse Species B Adenoviruses at US Military Recruit Training Centers.” Adenovirus outbreaks at military centers have been a problem that was controlled by a vaccination program using a live attenuated vaccine against Adenovirus 4 and 7. When the program stopped in the late 90’s, adenovirus infections returned and in the past several years Ad4 was dominant, but, as noted above, Ad14 was widely detected in a small portion of the patients in the spring of 2006.
Yesterday, the partial sequences of isolates from San Diego, Great Lakes, and Fort Benning were released. All three sequences were identical. Moreover, the report in MMWR on ad14 outbreaks in civilians in New York, Washington, Oregon as well as the outbreak at Lackland, indicated sequences from all four states were also identical. The partial sequences of just over 500 BP differed from the 1955 reference strain at two positions. One change matched the polymorphism found in a human ad38 isolate as well as a simian ad3 isolate.
A comparison of the data leading up to the 2007 outbreaks demonstrates how dramatic the emergence has been. As noted above, Ad14 was not seen in the earlier isolates from the various training centers. Even after it appeared in the five centers in the spring of 2006, it was still a minor serotype in the collections through the fall of 2006.
In the MMWR paper on the 2007 outbreaks, the Ad14 detection changed dramatically. At Lackland, 106 of the 118 Ad positive patients serotyped as Ad14 between February and June. Thus, Ad14 had become the dominant serotype. Moreover, the number of ARD cases continued to be detected at levels between 50-70 patients per week. In addition 6 health case workers were Ad14 positive as were 220 recruits at three other training centers in Texas.
The MMWR paper also detailed an outbreak in Oregon. 46 Ad positive patients were identified and 31 were Ad14 positive. However, the 15 patients that were not Ad14 positive were under 5 years of age, so all adults that were Ad positive serotyped as Ad14.
The concern over the high frequency of Ad14 infections was compounded by the case fatality rate. 22 of the 31 patients were hospitalized and 16 moved to the ICU where 7 died.
The large reservoir of AD14 at military bases and civilian clusters raise concerns as increased Ad infections are expected as cold and flu season begins.
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