Adenovirus sneak attacks during the H7N9 flu season
Sci China Life Sci
Adenovirus sneak attacks during the H7N9 flu season
XU Jun 1
LI Chen 1
WALLINE Joseph 0
YU XueZhong 1
0 Division of Emergency Medicine, Department of Surgery, Saint Louis University Hospital , Saint Louis, Missouri 63110 , USA
1 Chinese Academy of Medical Sciences, Peking Union Medical Hospital , Beijing 100730 , China
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The H7N9 influenza virus made headlines recently, with
outbreaks in Chinese urban centers. These infections
continue a recent trend of novel virus outbreaks, such as those
involving SARS coronavirus and the H1N1 influenza virus.
These outbreaks have been likened to tropical storms, and
like prior ‘viral storms’ the latest H7N9 influenza virus has
aroused public panic despite the fact that H7N9 infection
rates are sporadic. At the same time, other more common
ones (such as adenovirus) can lead to much more likely
pathology. Recently we admitted two patients with severe
adenovirus pneumonias in ARDS; both of them ICU-level
care, mechanical ventilation and special positioning to
maintain their oxygenation.
Adenoviruses are DNA viruses with no envelope, a
double-stranded DNA genome, and a 20-sided icosahedral
capsid composed of 252 capsomeres. They are widely prevalent
in humans, with over 100 types identified, of which more
than 60 can infect humans. Adenoviruses have caused
epidemics in China since the 1950s. Most recently, adenovirus
type 55 caused an outbreak in China’s Shanxi Province in
2006. American scientists found in 2009 that adenoviruses
could be transmitted from monkeys to humans and lead to
infection. In February 2012, a viral outbreak in China’s
Hebei Province was confirmed as adenovirus type 55.
Unlike H7N9, adenoviruses can be spread by droplets,
close personal contact or by fecal-oral routes. The general
population is susceptible, in particular infants and young
children, as well as the immunocompromised. Adenoviruses
can infect multiple organ systems, including the respiratory,
gastrointestinal, urinary, and ocular system. Its incubation
period is typically 4–5 d, and clinical manifestations differ
between virus types.
Adenoviral respiratory infections are common, generally
mild, and self-limiting with a natural course of about 7–10 d.
However, adenovirus types 7 and 55 can develop into
severe pneumonias with lung consolidation (Figure 1A).
Adenovirus ocular infections are often a complication of
adenovirus respiratory tract infections (Figure 1B).
At present, there is no specific treatment for adenovirus
infections. Symptoms of infection include fever, dry throat,
cough, difficulty breathing or gastrointestinal discomfort.
Therapy mainly includes non-specific antivirals, early
low-dose glucocorticoids, prophylactic use of antibiotics,
and organ support therapy. The lack of targeted antiviral
therapy makes the prevention of adenovirus infection
extremely important. The strict isolation of confirmed and
suspected cases, as well as maintaining rigorous personal
Figure 1 CT scan of adenovirus type 7 pneumonia with lung
consolidation (A) and conjunctivitis (right eye) in a doctor accidentally infected by
droplets from an adenovirus-infected patient (B).
and environmental hygiene will help to enhance resistance.
Although an adenovirus vaccine containing
formaldehydeinactivated virus has been developed, it has not yet been
widely used because of its apparent carcinogenicity in
animal test subjects.
The infectivity and virulence of adenoviruses are high,
but can be controlled. Hospitalization is often required for
those with severe adenovirus infections. All medical
institutions should take precautions against this virus, and
maintain a high degree of vigilance for infections, especially
when other viruses such as H7N9 are commanding so much
attention.
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