Adenovirus pneumonia

How often adenovirus causes pneumonia

Viruses are often found in children with community-acquired pneumonia: in 45–66% of children, according to the various studies cited in clinical guidelines [2]. In a large US study of children hospitalized with pneumonia, adenovirus was found in 15% of children under 5 and in 3% of older children [2].

In children from 3 months to 5 years old, viruses, including adenoviruses, are one of the main causes of pneumonia. In older children and teenagers, viral pneumonias are rare and usually relatively mild [2].

In adults, viral pneumonias are mild in most cases. But in older people and in people with lung disease, heart disease or immunodeficiency they can lead to severe complications [6].

Who is at risk

• infants [2] [3];
• people with weakened immunity [2] [1];
• people with chronic lung or heart disease [7];
• young people living in close quarters, such as the military: outbreaks occur among them, usually with tracheobronchitis and sometimes with pneumonia [3].

According to the MSD Manual, even severe primary adenovirus pneumonia is usually not fatal. The exception is rare fulminant (very rapid) cases, mainly in infants, military recruits and people with immunodeficiency [3].

Which types are more dangerous

Type 7 is recognized as an important cause of severe respiratory infections in adults in the US [8]. In 2006–2007, type 14 caused severe, sometimes fatal infections, including in healthy young adults [9]. In children, types 3, 7 and 21 are usually behind a rare complication called bronchiolitis obliterans [10]. Read more in the article adenovirus types.

How to suspect pneumonia

Pneumonia is inflammation of the lung tissue. Clinical guidelines describe it as a combination of general signs of illness (intoxication), breathing problems, changes the doctor hears in the lungs, and a shadow on the chest X-ray [2].

With adenovirus infection, a high fever lasts longer than with most respiratory viruses, up to 5–7 days [4], and a cough in adults can last 2 weeks or longer, up to a month [5]. So a long fever by itself does not mean pneumonia; a doctor needs to check the lungs.

In children under two, a viral infection of the lower airways usually takes the form of bronchiolitis, which is almost impossible to tell apart from viral pneumonia by symptoms or on an X-ray [2].

Diagnosis

• A diagnosis of pneumonia requires an infiltrate (a shadow) on the chest X-ray [2]. Increased lung markings or widened lung roots alone are not enough for the diagnosis and are not a reason for antibiotics [4].
• With adenovirus infection, blood tests can look like a bacterial infection: white blood cells can reach 15–20 × 10⁹/L or even higher, and C-reactive protein can be above 30 mg/L [4].
• When needed, more often in the hospital, adenovirus is detected with a rapid test (throat swab, nasal wash) or PCR of a nasopharyngeal swab [4] [1].
• The ICD-10 code is J12.0, "Adenoviral pneumonia" [11].

Treatment

There is no specific treatment for adenovirus infection and no FDA-approved antiviral drugs [1]. Treatment is symptomatic and supportive [3].

There are no antiviral drugs with proven effectiveness [3]. The MSD Manual mentions cidofovir as the drug most likely to have an effect [3]; the decision to use it is made by a doctor. Whether antibiotics are needed is decided by a doctor based on the examination.

Long-term effects

A rare but serious complication in children is post-infectious bronchiolitis obliterans. It is a chronic condition: fibrosis (scarring) develops in the small airways, the bronchioles become blocked, and it can lead to disability [10].

It may be suspected if shortness of breath and signs of airway obstruction last 6 weeks or longer, or come back after a period of improvement, and if respiratory failure worsens along with a persistent fever during adenovirus infection [10].