by using a previously described dna restriction analysis procedure ( 7 ) , we studied 76 archived adenovirus isolates collected among influenzalike - illness surveillance sites across iowa from 1992 to 2002 . among the 76 isolates , 40 ( 53% ) were ad7d2 , and 6 ( 8% ) were ad7h ( figure ) .
the first ad7d2 specimen was isolated in march 1994 from a child living in south - central iowa .
the first ad7h specimen was isolated in november 1993 from a child living in north - central iowa .
number of adenovirus ( ad ) isolates collected in iowa during influenzalike - illness surveillance by genome type and year .
ad7d2 caused illness among patients in iowa ranging in age from 3 months to 49 years .
although the clinical details are sparse , a number of patients were thought to have influenza or were diagnosed with respiratory distress syndrome .
at least 4 children from an ad7d2 october 2000 epidemic at a long - term care facility in des moines , iowa , died .
ad7d2 became increasingly more prevalent across iowa , displacing ad7b , the predominant genome type circulating in the united states since the early 1970s ( 8) . in 2002 , data suggest that ad7d2 supplanted all other ad7 genome types ( 9 of 9 ad7 isolates were a7d2 ) ( figure ) .
ad7d2 was first detected in israel in 1992 ; beginning in 1995 , it was associated with epidemics of unusually severe respiratory disease with high fevers among children in japan ( 9,10 ) .
ad7h was first detected in south america in 1986 ; since then it has supplanted the previous most prevalent genome type , ad7c , in chile , uruguay , argentina , and possibly other countries ( 11 ) .
ad7h has caused pediatric respiratory epidemics , and infected children had longer hospitalizations , had higher temperatures , and required more supplemental oxygen ( 12 ) . in at least 1 study , up to 94% of adenovirus deaths were attributed to ad7h ( 11 ) . whether these strains are truly more virulent or whether they better evade the host s immune system is a matter for future study .
what does seem to be clear is that a simple mutation ( ad7d2 ) ( 9 ) or recombination ( ad7h ) ( 13 ) may generate new adenovirus strains that could result in more epidemics and higher death rates .
the number of immunocompromised patients in the united states is increasing , and they , in addition to young children , may be at increased risk for severe disease from emergent adenovirus strains .
developing molecular typing strategies for emerging ad strains seems prudent , as does improving local and national surveillance for adenovirus illness .
considering adenovirus to be a potential nosocomial pathogen seems wise , and researchers should seek to identify effective antiviral therapy for outbreak interventions .
these actions will help public health officials better understand the changing epidemiology of adenovirus infections . because of increased adenovirus morbidity ( 14,15 ) , the u.s .
department of defense recently contracted to again produce ad4 and ad7 vaccines for military trainees .
if civilian populations were identified to be at high risk for serious ad4 or ad7 disease , they might also benefit from these vaccines .
 we evaluated 76 adenovirus type 7 ( ad7 ) isolates collected in iowa from 1992 to 2002 and found that genome type ad7d2 became increasingly prevalent . by 2002 
 , it had supplanted all other ad7 genome types . 
 the association of ad7d2 with severe illness and death calls for heightened public health concern . 
The Study
Conclusions