Adenovirus infection Adenovirus infections most commonly cause illness of the respiratory system; however, depending on the infecting serotype, they may also cause various other illnesses, such as gastroenteritis, conjunctivitis, cystitis, and rash illness. Symptoms of respiratory illness caused by adenovirus infection range from the common cold syndrome to pneumonia, croup, and bronchitis. Patients with compromised immune systems are especially susceptible to severe complications of adenovirus infection.
Acute respiratory disease (ARD), first recognized among military recruits during World War II, can be caused by adenovirus infections during conditions of crowding and stress. Recently, several adenoviruses, especially adenovirus 36 (AD-36), have been shown to cause obesity in animals, and are associated with human obesity. [1][2] Diagnosis Antigen detection, polymerase chain reaction assay, virus isolation, and serology can be used to identify adenovirus infections.
Adenovirus typing is usually accomplished by hemagglutination-inhibition and/or neutralization with type-specific antisera. Since adenovirus can be excreted for prolonged periods, the presence of virus does not necessarily mean it is associated with disease. Treatment Most infections are mild and require no therapy or only symptomatic treatment. Because there is no virus-specific therapy, serious adenovirus illness can be managed only by treating symptoms and complications of the infection. Deaths are exceedingly rare but have been reported. 4] Prevention Safe and effective adenovirus vaccines were developed for adenovirus serotypes 4 and 7, but were available only for preventing ARD among US military recruits,[5] and production stopped in 1996. [6] Strict attention to good infection-control practices is effective for stopping nosocomial outbreaks of adenovirus-associated disease, such as epidemic keratoconjunctivitis. Maintaining adequate levels of chlorination is necessary for preventing swimming pool-associated outbreaks of adenovirus conjunctivitis. Adenovirus serotype 36
Human adenovirus 36 (HAdV-36) or AD-36 is one of 52 types of adenoviruses known to infect humans. AD-36 was first isolated in 1978 from the feces of a girl suffering from diabetes and enteritis,[1] and has long been recognized as a cause of respiratory and eye infections in humans. [2] It was first shown to be associated with obesity in chickens by Dr. Nikhil Dhurandhar. [3][4] There has been a positive correlation between body fat and the presence of AD-36 antibodies in the blood [5]. Previous research showed that chicken or mice injected with similar types of viruses show a statistically significant weight gain. 3] To date, AD-36 is the only human adenovirus that has been linked with human obesity, present in 30% of obese humans and 11% of nonobese humans. [6] In addition, a study of obese Americans indicates that about 30% of the obese individuals and only 5% of non-obese individuals have antibodies to Ad-36. [7] AD-36 also causes obesity in chickens, mice, rats, and monkeys. [6] Adenoviruses| Transmission electron micrograph of two adenovirus particles| Virus classification| Group:| Group I (dsDNA)| Family:| Adenoviridae| | Genera| Atadenovirus Aviadenovirus Ichtadenovirus
Mastadenovirus Siadenovirus| AD-36 infection can induce cellular differentiation of 3T3-L1 preadipocytes and stem cells derived from human adipose tissue Adenoviridae Adenoviruses are medium-sized (90–100 nm), nonenveloped (naked) icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome. There are 53 described serotypes in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well. Viruses of the family Adenoviridae infect various species of vertebrates, including humans.
Adenoviruses were first isolated in human adenoids, from which the name is derived, and are classified as group I under the Baltimore classification Virology Classification This family contains the following genera: * Genus Atadenovirus; type species: Ovine adenovirus D * Genus Aviadenovirus; type species: Fowl adenovirus A * Genus Ichtadenovirus; type species: Sturgeon adenovirus A * Genus Mastadenovirus; type species: Human adenovirus C; others include AD-36 * Genus Siadenovirus; type species: Frog adenovirus Structure
Adenoviruses represent the largest nonenveloped viruses, because they are the maximum size able to be transported through the endosome (i. e. envelope fusion is not necessary). The virion also has a unique “spike” or fiber associated with each penton base of the capsid (see picture below) that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host cell. Genome chematic diagram of the linear adenovirus genome, showing Early genes (E) and Late genes (L). The adenovirus genome is linear, non-segmented double stranded (ds) DNA which is between 26 and 45 Kbp.
This allows the virus to theoretically carry 22 to 40 genes. Although this is significantly larger than other viruses in its Baltimore group it is still a very simple virus and is heavily reliant on the host cell for survival and replication. An interesting feature of this viral genome is that it has a terminal 55 kDa protein associated with each of the 5′ ends of the linear dsDNA, these are used as primers in viral replication and ensure that the ends of the virus’ linear genome are adequately replicated. Epidemiology Transmission
Adenoviruses are unusually stable to chemical or physical agents and adverse pH conditions, allowing for prolonged survival outside of the body and water. Adenoviruses are primarily spread via respiratory droplets, however they can also be spread by fecal routes as well. Humans * See Adenovirus infection * See Adenovirus serotype 14 Animals Two types of canine adenoviruses are well known, type 1 and 2. Type 1 causes infectious canine hepatitis, a potentially fatal disease involving vasculitis and hepatitis. Type 1 infection can also cause respiratory and eye infections.
Canine adenovirus 2 (CAdV-2) is one of the potential causes of kennel cough. Core vaccines for dogs include attenuated live CAdV-2, which produces immunity to CAdV-1 and CAdV-2. CAdV-1 was initially used in a vaccine for dogs, but corneal edema was a common complication. [4] Adenoviruses are also known to cause respiratory infections in horses, cattle, pigs, sheep, and goats. Equine adenovirus 1 can also cause fatal disease in immunocompromised Arabian foals, involving pneumonia and destruction of pancreatic and salivary gland tissue. [4] Prevention
Main article: Adenovirus vaccine In the past, US military recruits were vaccinated against two serotypes of adenotypes, with a corresponding decrease in illnesses caused by those serotypes. The vaccine is no longer manufactured, and there are currently no vaccines available to protect against the adenovirus. Good hygiene, including handwashing, is still the best way to avoid picking up the adenovirus from an infected person. Infections Main article: Adenovirus infection Most infections with adenovirus result in infections of the upper respiratory tract.
Adenovirus infections often show up as conjunctivitis, tonsilitis (which may look exactly like strep throat and cannot be distinguished from strep except by throat culture), an ear infection, or croup. Adenoviruses can also cause gastroenteritis (stomach flu). A combination of conjunctivitis and tonsilitis is particularly common with adenovirus infections. Some children (especially small ones) can develop adenovirus bronchiolitis or pneumonia, both of which can be severe. In babies, adenoviruses can also cause coughing fits that look almost exactly like whooping cough.
Adenoviruses can also cause viral meningitis or encephalitis. Rarely, adenovirus can cause cystitis (inflammation of the urinary bladder—a form of urinary tract infection—with blood in the urine). Most people recover from adenovirus infections by themselves, but people with immunodeficiency sometimes die of adenovirus infections, and—rarely—even previously healthy people can die of these infections. [5] Adenoviruses are often transmitted by coughed-out droplets, but can also be transmitted by contact with an infected person, or by virus particles left on objects such as towels and faucet handles.
Some people with adenovirus gastroenteritis may shed the virus in their stools for months after getting over the symptoms. The virus can be passed from one person to another through some sexual practices, and through water in swimming pools that do not have enough chlorine in them. As with many other illnesses, good handwashing is one way to lessen the spread of adenoviruses from one person to another. Heat and bleach will kill adenoviruses on objects.
