Adenovirus

What is an Adenovirus Infection?

Adenoviruses are a family of viruses. These may cause infections in humans as well as animals. The most common infections caused by adenoviruses are respiratory tract infections.

What are the symptoms of adenovirus infection?

Adenovirus often infects the airways and the intestinal tract. An infection usually manifests with symptoms similar to a common cold. There is a sore throat, runny nose and eyes, sneezing, headaches, cough and fever.

In some persons infection with adenovirus may also cause croup or bronchitis. Some infections may also lead to conjunctivitis (pink-eye), skin rash, diarrhea and bladder infections.

Incubation period

For an airway infection it takes around 2 to 14 days for the symptoms to appear after exposure to the virus. This is called the incubation period. For intestinal infections the incubation period is 3 to10 days.

How long does adenovirus infection last?

The illness commonly does not last beyond three to five days and may last a week. Serious infections may debilitate a person for a couple of weeks.

Complications of adenovirus infection

Some persons with a poor immunity are prone to develop complications due to adenovirus infection.

Common but serious complications include lung infection or pneumonia, middle ear infection or otitis media and brain infections or meningitis.

Who can be affected with adenovirus?

Adenovirus may affect any person. In a healthy person the infection is usually mild and resolves on its own within a week.

Those with an immature or weak immune system are more at risk of severe complications. This includes young children and infants, elderly, pregnant women and those with a suppressed immunity (HIV AIDS patients, those on cancer chemotherapy drugs or immunosuppressant drugs after organ transplants etc.).

Outbreaks are common among those living in closed quarters like prisons, schools, hostels etc.

How does adenovirus spread?

Spread may occur in two manners. The virus can be carried in airborne droplets that are released when an infected person coughs or sneezes.

This virus may also survive for long durations on objects. This spread is also possible if the objects used by an infected person are touched or an infected person handles food or other items used by un-infected persons.

Infection can also spread by touching the eyes, nose, or mouth with contaminated hands that have not been washed well. Drinking from contaminated water sources may also spread the infection.

Diagnosis and treatment of adenovirus infection

Usually symptoms are used to diagnose adenovirus infections. There are however laboratory serological tests that help in the diagnosis of adenovirus infections. These tests are useful during outbreaks of this infection.

There is no adenovirus-specific therapy and the infection usually resolves by itself. Complications however may be treated with specific antibiotic therapy.

Patients with uncomplicated infections are usually advised bed rest, isolation, good hygiene (to prevent spread), over-the-counter fever relieving medicine (e.g. Acetaminophen/Paracetamol) and plenty of fluids.

In case of a severely blocked or runny nose cool-mist humidifiers and an airway dilator medication may be advised.

Adenovirus Infection Diagnosis

Adenovirus infections are most commonly diagnosed based on the symptoms of the condition.

Symptoms of adenovirus infection

The infection commonly manifests as an airway infection or an intestinal infection.

For an airway infection it takes around 2 to 14 days for the symptoms to appear after exposure to the virus. This is called the incubation period. For intestinal infections the incubation period is 3 to10 days.

Symptoms of an airway infection include:-

  • sore throat
  • runny nose
  • redness and inflammation of the conjunctiva of the eyes (pink eyes)
  • sneezing
  • cough
  • headaches
  • fever
  • chills
  • croup or noisy breathing
  • bronchitis

Some infections may also lead to skin rash, diarrhea and bladder infections.

The illness commonly does not last beyond three to five days and may last a week. Serious infections may debilitate a person for a couple of weeks.

Common but serious complications include lung infection or pneumonia, middle ear infection or otitis media and brain infections or meningitis.

Laboratory diagnosis of adenovirus

Laboratory diagnosis is available for detection of adenovirus. These are particularly useful for detecting and preventing large outbreaks.

Some of the laboratory diagnostic techniques include:-

  • Antigen detection

    The adenovirus, like other viruses, contains numerous proteins on its surface. Within the body these act as antigens against which several antibodies are formed. This helps the body to fight off an adenovirus infection. For example, the core of the particle contains at least 4 proteins called the TP (Terminal Protein), V, VII and Mu, a small protein.

  • Polymerase chain reaction assay

    These can be used to identify the viral nuclear material or the viral DNA. Adenovirus has a double stranded linear DNA genome of length 36-40 kilo basepairs (kbp).

  • Virus isolation

    The intact adenovirus particles may be isolated from samples of mucous, stool, blood and urine of an infected person. Once isolated the virus is usually types into subgroups and types. Virus isolation may also require virus cell cultures. Adenovirus typing is usually done by hemagglutination-inhibition and neutralization with type-specific antisera or by molecular methods.

  • Serology tests

    These tests utilize measures to assess the levels of the antibodies that have been generated against an active infection with adenovirus.

Adenovirus Infection Treatment and Prevention

Adenovirus infection treatment

Like most other viral infections, there are no specific drugs that can target the adenovirus. The body’s immune system fights the infection and it resolves in three to five days in most individuals.

Treatment is targeted towards reliving symptoms of the condition and includes:-

  • Bed rest and isolation to prevent spread of infection.
  • Drinking plenty of water and clear fluids. This prevents dehydration.
  • Over the counter fever relievers may be taken in case of fever and headache. Paracetamol/Acetaminophen or Ibuprofen is most commonly used. In children below 12 years Aspirin should not be used to relieve fever. Use of Aspirin in viral infections raises the risk of liver and brain damage called Reye’s syndrome in children.
  • Humidifiers may be prescribed to ease a sore throat and blocked nose. Saline nasal drops may also be used. In patients with asthma, if there is difficulty in breathing medications (inhalers) that can dilate the airways are prescribed.
  • Lozenges and cough drops may be taken to ease the throat and cough.
  • In those with conjunctivitis eye drops with antibiotics and ointments are advised.
  • Complications such as pneumonia need to be managed in the hospital after admission. Appropriate antibiotics, oxygen, intravenous fluids etc. are needed.
  • Those with meningitis also need to be admitted to the hospital and managed with antibiotics, oxygen, intravenous fluids etc.
  • Those with middle ear infections or otitis media may be managed on an outpatient basis with use of antibiotics and supportive treatment for pain, fever and other symptoms.
  • Cidofovir is an antiviral agent that has been used to treat severe adenovirus infections in people with suppressed or low immune systems. Cidofovir is given three times a week at the dose 1mg/kg/day. Cidofovir may alternatively by given at a dose of 5mg/kg/week. This drug can damage the kidneys and is also expensive. It is reserved for only serious cases. Cidofovir should be stopped when adenovirus is no longer detected in the blood by PCR in two consecutive samples.
  • Serious patients especially with lowered immunity may also be given immunoglobulin at a dose of 500mg/kg weekly for 3 weeks to fight the infection.

Prevention of adenovirus infection

Prevention of adenovirus infection relies on healthy habits applicable for prevention of most viral infections. These measures include:-

  • Hand washing before and after eating or handling material used by an infected person. Alcohol-based hand sanitizers may be used frequently if hands are not visibly dirty.
  • Eyes, nose or mouth should not be touched using contaminated hands or fingers.
  • Covering mouth and nose with a tissue when coughing or sneezing helps prevent spread of the virus.
  • Isolation and avoidance of work or school when ill with a cold or viral infection.
  • Keeping swimming pools adequately chlorinated.
  • Avoiding sharing towels and utensils etc. with an infected person. Avoidance of close contact with a person ill with adenovirus infection.

Adenovirus vaccine

An oral vaccine against adenovirus types 4 and 7 was approved by the U.S. Food and Drug Administration in March 2011 for U.S. military personnel. It can be used only in those between 17 and 50 years of age.

The vaccine is recommended by the U.S. Department of Defense for military recruits to prevent acute respiratory disease.

Adenovirus Infection Epidemiology

Adenovirus outbreaks are not very common in the United States, however, they do occur and since the virus is capable of spreading very fast, the outbreaks may achieve large proportions before being contained.

Respiratory tract infections and conjunctiva infections with adenovirus are seen. The commonest time of an outbreak of adenovirus infection is during late winter, spring, and early summer, but infections may occur all year round.

Adenovirus types commonly linked to acute respiratory infections

Adenovirus types that are commonly linked to the outbreaks are those that are more virulent and likely to spread.

These include Adenovirus types 3, 4 and 7 that commonly lead to acute respiratory infections. These may spread widely among populations within a few weeks.

The spread is common via droplets of water that are coughed or sneezed out by an infected person. These droplets are tiny, nearly invisible to the naked eye and carry the virus particle. These are then inhaled by healthy persons.

Spread is more common among those living in close quarters including schools, prisons, hostels, barracks etc. One of the strains, adenovirus type 14, has been particularly associated with several outbreaks of acute respiratory illness among U.S. military recruits and the general public since 2007.

Adenovirus types commonly linked to conjunctival infections

Adenovirus types 8, 19, 37, 53 and 54 are more likely to cause conjunctival infections leading to severe redness, pain and watering of the outer membrane that lies like a film over the eyes.

Adenovirus infection of the conjunctiva is termed adenoviral keratoconjunctivitis. Conjunctivitis due to adenovirus may spread to large populations like an epidemic in a very short period of time.

It is also spread by persistence of the virus in the objects used by an infected person. For example, when an infected person touches a surface with his or her hands that have touched his or her eyes and have not been washed adequately, he or she leaves the virus on the object. This when touched by another healthy person can be picked up.

Adenovirus types commonly linked to gastrointestinal tract infections

Enteric adenovirus types 40 and 41 are known to cause gastrointestinal tract infections especially among children.

Adenovirus infection among swimmers

Adenovirus 4 and 7 can spread in water of swimming pools that have not been chlorinated adequately. This can cause conjunctivitis among swimmers.