Adenovirus

Definitions & Key takeaways

Adenovirus is a type of DNA virus that can cause respiratory infections, including the common cold, and also conjunctivitis or "pink eye." They can also cause more serious diseases such as pneumonia, bronchitis, and even meningitis, especially in immunocompromised individuals.

Adenovirus is spread through contact with respiratory secretions, such as saliva or mucus, from an infected person. They can also be spread through the fecal-oral route, and hand hygiene with water and soap or using sanitizers is the best way to prevent infection with adenovirus.

Watch video only
Adenoviruses are a group of viruses that cause respiratory, gastrointestinal, and genitourinary infections. There are about 60 serotypes of the virus, divided into 7 subgroups, from A to G.
Common respiratory infections caused by adenoviruses include a sore throat, the common cold and pneumonia, whereas diarrhea is the most common gastrointestinal ailment.
Adenoviruses can also cause cystitis, which is the inflammation of the bladder, as well as eye conditions like conjunctivitis.
Adenoviruses are double-stranded linear DNA viruses surrounded by an icosahedral capsid, which is a spherical protein shell made up of 20 equilateral triangular faces.
And they’re “naked” because the capsid isn’t covered by a lipid membrane. Their capsid is unique among viruses because it has fiber-like projections from each of the 12 vertices of the shell.
Adenovirus is primarily transmitted by respiratory droplets when someone coughs or sneezes and by the fecal-oral route. In other words, you catch it by ingesting the stool or vomit particles of someone who is sick.
Yuck. This can happen if infected stool ends up in the water supply or on agricultural fields, if flies land on it, and transfers stool particles to other places, or by touching contaminated surfaces.
You can summarize it as the four Fs: fluids, fields, flies, and fingers. As a result, adenovirus can end up in food and drinking water.
Two less common modes of transmission are from mother to newborn via the cervical fluid in the birth canal, and following an organ transplant from a donor who has an adenovirus infection.
After entering the body, the virus heads for epithelial cells, like those that make up the respiratory, GI, or urinary mucosa, where it uses its fiber projections to bind to the coxsackie-adenovirus receptor on cell membranes.
This allows it to get inside the cells. Once inside, adenovirus has multiple cytopathic, or cell-damaging, effects, like blocking synthesis of cellular DNA and the production of proteins.
This results in cell death by lysis, or the breakdown of the cell membrane, which elicits an inflammatory response from the host.
Namely, leukocytes found in the affected tissue release inflammatory mediators like histamine and cytokines. This makes blood vessels in the infected zone dilate and become more permeable, allowing more leukocytes and fluid to enter local tissue to fight the infection.
This translates into the four cardinal signs of inflammation: heat, pain, redness, and swelling. Now, different serotypes of adenovirus prefer different types of epithelial cells, so the impacts of adenovirus infection on the body will vary.
Some serotypes prefer the upper respiratory tract, causing infectious rhinitis, also known as the common cold, pharyngitis, which is the inflammation of the mucous membrane of the pharynx, or tonsillitis, when the tonsils are inflamed.
If the virus moves into the lower respiratory system, it can cause pneumonia. Some serotypes prefer the epithelial cells of the GI tract, particularly those of the small intestine, causing gastroenteritis.
Other serotypes prefer the urinary tract, resulting in hemorrhagic cystitis, or inflammation of the bladder associated with bloody urine.
Lastly, adenovirus infection can affect the conjunctiva, which is the mucous membrane of the eye and inner eyelids, resulting in conjunctivitis, more commonly called pink eye.
A particular type of adenovirus infection called epidemic keratoconjunctivitis also causes preauricular lymphadenopathy, which is inflammation of the lymph nodes located right where the ear meets the cheek, because they receive the fluid that drains from the conjunctiva and the inner eyelids.
In most cases, adenovirus is confined to the epithelial cells of its original infection site, but it can sometimes break through the mucosa and spread to other parts of the body, causing a disseminated infection.
Ok, now adenovirus is very contagious and resistant, so it’s easy to catch and outbreaks are common. As a result, it spreads quickly in close-quarter settings like military barracks, hospitals, summer camps, and daycares.
It’s more common in children and military recruits, and it’s also particularly dangerous for immunocompromised individuals.
Many adenovirus infections are asymptomatic, but when there are symptoms they are acute and usually show up after an incubation period that can vary from 2 to 14 days.
Upper respiratory infection symptoms include fever, nasal congestion and runny nose, and a sore throat. Lower respiratory infections might be accompanied by coughing, shortness of breath, and chest pain.
Symptoms of gastrointestinal adenovirus infection include fever, nausea, vomiting, and watery diarrhea. Hemorrhagic cystitis presents with frequent and painful urination, bloody urine, and lower abdominal pain.
Conjunctivitis symptoms, which last anywhere from a few days to several weeks in the case of epidemic keratoconjunctivitis, include eye irritation, soreness, and redness, sensitivity to light - or photophobia, and excessive tearing.
When conjunctivitis, fever, pharyngitis, and inflammation of lymph nodes in the neck are all present, this is called pharyngoconjunctival fever.
Disseminated adenovirus infection, where the virus spreads to multiple organs, is a complication that mostly affects immunocompromised individuals and has a high mortality rate.
Adenovirus infection is usually diagnosed simply by clinical examination. In the case of an outbreak or of someone with particularly severe symptoms, the diagnosis can be confirmed with a viral culture, adenovirus-specific viral antigen assays, and polymerase chain reaction assays that look for the viral DNA.
Fortunately, most adenovirus infections are mild, and improve with hydration and a few days of rest. In severe cases, like adenovirus infections in immunocompromised individuals, antivirals like cidofovir or immunotherapy like intravenous immune globulin may be given.
Finally, there is a live vaccine for adenoviruses, but it’s only given to people at high risk of getting the infection, like soldiers living in military barracks.
The safety of the vaccine has not yet been evaluated in children. Other preventive measures include proper water and sanitation facilities, which block fecal-oral transmission by fluids, flies, and fields - 3 of the 4 F’s.
Hand washing with antiseptic soap and water and sanitizing surfaces that would’ve come into contact with respiratory droplets or stool can prevent transmission by fingers.
All right, as a quick recap… Adenoviruses are double-stranded linear DNA viruses with some 60 serotypes of the virus. The virus infects epithelial cells, where it causes structural changes that result in cell death from lysis and prompts an inflammatory response by the host.
It’s transmitted by respiratory droplets, the fecal-oral route, cervical fluid, and via organ transplants. It can affect the respiratory system, causing pharyngitis, rhinitis, and pneumonia, the gastrointestinal system, causing gastroenteritis, the genitourinary system, causing hemorrhagic cystitis, and the eyes, causing conjunctivitis.
Symptoms vary based on which system is infected. Treatment is usually supportive, except in severe cases or for immunocompromised individuals, when antivirals and immunotherapy might be given.