Adenoviruses are DNA viruses with high pathogenic power. They cause respiratory infections in subjects of any age but most commonly in frail and immunocompromised adults and in the paediatric population, particularly young children and infants. Adenoviruses can manifest with symptoms similar to the common cold, including rhinorrhoea, fever, cough and sore throat; the evolution of these into clinical manifestations such as bronchitis, bronchiolitis and pneumonia can be serious and even fatal. Respiratory infections are most common in late winter, spring and early summer. But these infections can occur at any time throughout the year.
The viral infection mainly affects the respiratory system (cold, pharyngitis, tonsillitis, bronchitis, pneumonia), but also the uro-genital system with clinical manifestations such as cystitis. Adenoviruses can cause conjunctivitis, gastroenteritis and/or diarrhoea of the gastro-intestinal tract. More rarely, they can affect the liver with liver failure, the heart with endocarditis, and the nervous system with meningitis and encephalitis.
How is Adenovirus caught and transmitted?
It can be easily transmitted by an infected person through sneezing or coughing resulting in the release of secretions or droplets of saliva into the environment, or through theingestion of food contaminated with infected bodily secretions. Adenoviruses are very resistant in the environment, so transmission is easier in crowded and convivial environments (schools, canteens, public transport, etc.). In fact, infection occurs by coming into contact with contaminated surfaces or objects.
How long can you be contagious for?
Adenoviruses are transmitted by an infected person during the manifestation phase of clinical symptoms. Affected patients may also be asymptomatic, elimination of the virus by patients with an asymptomatic respiratory or gastrointestinal infection can continue for months, or even years. Adenoviruses are very resistant to the external environment.
What are the symptoms of adenovirus?
Adenoviruses infect the respiratory system causing symptoms similar to a flu-like condition with:
- cold,
- cough,
- sore throat,
- fever.
If overlooked, the infection can cause more serious symptoms affecting the lower airways with a diagnosis of bronchitis, or bronchiolitis. Several other diseases may be associated with Adenovirus infections such as conjunctivitis, gastroenteritis, cystitis, myocarditis, cardiomyopathy and meningoencephalitis.
Symptoms: children
Infection can occur in children of any age. Children between the ages of 6 months and 2 years who attend nurseries are more likely to become ill with these viruses. Adenovirus infections of the digestive tract are more common in children under the age of 5 years. Most children have experienced at least one Adenovirus infection by the age of 10 years. In children, symptomatic infections occur with upper airway symptoms, including:
- pharyngitis,
- otitis media,
- cough,
- exudative tonsillitis with cervical adenopathy that can be difficult to distinguish from streptococcal pharyngitis group A.
Epidermal kerato-conjunctivitis, which causes redness, burning and discomfort in the affected eye, is also widespread in children.
Symptoms: adults and the elderly
Adenovirus infection, in adults and the elderly, initially manifests itself with disorders affecting the upper respiratory tract about 3–10 days after first contact with the virus. Typical symptomatology involves:
- rhinitis,
- pharyngitis,
- enlargement of the tonsils,
- enlarged neck lymph nodes (in the case of an acute respiratory infection),
- fever.
If overlooked in the early stages,Adenovirus causes infection of the innermost airways, resulting in bronchiolitis or pneumonia. Adenovirus infection can affect the intestine, manifested by symptoms such as vomiting, diarrhoea and abdominal pain.
Adenovirus: diagnosis and tests to be carried out?
From blood sampling, it is possible to investigate the antibody response with serological measurement of IgG and IgM immunoglobulins.
IgM are the first antibodies to be produced, and traces of it are found in the blood 5–10 days after contact with a foreign agent. IgG production generally increases within a few weeks of infection and gradually decreases until it stabilises.
It is possible to investigate the presence of the virus directly, by looking for the presence of the nucleic acid of the nasopharyngeal virus swab. Swab analysis allows the presence of Adenovirus to be detected even at low concentrations and is the preferred method of investigation for early and accurate diagnosis, even before the appearance of the antibody response.
Dr Angela Marano
Specialist in Pathology and Clinical Biochemistry
