OVERVIEW

What is adenovirus pneumonia?

Adenovirus pneumonia refers to pneumonia caused by adenovirus infection.

Pneumonia is an infection in the lungs that can be caused by bacteria or viruses, leading to symptoms such as cough, fever, and difficulty breathing. Adenovirus pneumonia is a type of viral pneumonia.

Is adenovirus pneumonia common?

Adenovirus infections are very common and often occur sporadically without a distinct seasonal pattern. Outbreaks have been reported worldwide in communities, closed or crowded environments (e.g., dormitories, healthcare facilities), and among military recruits [1]. Adenoviruses account for 5%-10% of febrile illnesses in infants and young children. Nearly all adults have experienced at least one type of adenovirus infection.

Adenovirus pneumonia is more common in children. Among children hospitalized for pneumonia, the adenovirus positivity rate is about 15% in those under 5 years old, and around 5% in older children. In adults with pneumonia, the adenovirus positivity rate is approximately 1%. Some studies suggest that adenovirus is only associated with pneumonia in children under 2 years old. This means that in patients aged 2 and above (including adults), even if adenovirus is detected, it may not be the cause of pneumonia [2].

Which department should I visit for adenovirus pneumonia?

If an adult develops adenovirus pneumonia, they can visit the respiratory medicine or infectious diseases department in a general hospital.

If a child develops adenovirus pneumonia, they can visit the pediatric department in a children's hospital or a general hospital.

If fever is present, they can visit the fever clinic in a general hospital.

SYMPTOMS

What are the common manifestations of adenovirus pneumonia?

Adenovirus pneumonia typically presents with high fever (temperature above 38.5°C), along with symptoms such as cough, wheezing, rapid breathing, and chest tightness. Other possible symptoms include sore throat, runny nose, conjunctivitis (also known as "pink eye"), and hoarseness.

Mild cases usually resolve within 7–11 days, with fever subsiding and other symptoms disappearing.

In severe cases, high fever may persist for 2–4 weeks, and some patients may experience temperatures exceeding 40°C. In children, pneumonia tends to be more severe in infants than in older children, potentially causing lethargy, irritability, seizures, drowsiness, diarrhea, or vomiting. Occasionally, extrapulmonary complications may occur, including meningoencephalitis, hepatitis, myocarditis, nephritis, and neutropenia. Critically ill patients may develop shock, respiratory failure, disseminated intravascular coagulation (DIC), or even death [3,4].

What are the common complications of adenovirus pneumonia?

(1) Respiratory failure: Manifested as rapid breathing, nasal flaring, breathlessness, cyanosis (bluish lips), and marked retractions of the neck and intercostal spaces during inspiration (medically termed "three depressions sign"—suprasternal, supraclavicular, and intercostal retractions).

(2) Acute respiratory distress syndrome (ARDS): Characterized by refractory hypoxia. Chest CT or X-ray may show diffuse bilateral pulmonary infiltrates, often referred to as "white lung."

(3) Pneumomediastinum or subcutaneous emphysema: Gas accumulation in the mediastinum or subcutaneous tissues. This is more likely in children with airway obstruction due to necrotic debris or mucus plugs, or those with asthma.

(4) Gastrointestinal dysfunction: Symptoms include diarrhea and vomiting; severe cases may progress to toxic intestinal paralysis or gastrointestinal failure.

(5) Toxic encephalopathy or encephalitis: Manifested as lethargy, drowsiness, irritability, or alternating agitation and listlessness. Severe cases may involve convulsions or coma.

(6) Sepsis: Adenovirus can cause viral sepsis, a systemic inflammatory response dysregulation. It not only leads to severe lung infection and injury but also extrapulmonary organ damage and dysfunction.

(7) Others: Hemophagocytic lymphohistiocytosis (HLH), liver injury, bone marrow suppression, myocarditis, etc. [3].

Can adenovirus pneumonia cause sequelae?

Young children with adenovirus pneumonia may develop pulmonary sequelae, including bronchiectasis and bronchiolitis obliterans. Among children under 5 years old, adenovirus infection carries the highest risk of long-term complications [2].

• Bronchiectasis: Refers to irreversible dilation and distortion of bronchi due to structural damage. Typical symptoms include chronic cough, copious purulent sputum, and recurrent hemoptysis. Currently, medications cannot reverse permanent bronchial wall damage. However, surgical removal of localized bronchiectasis may be an option for some patients.

• Bronchiolitis obliterans: Associated with small airway injury, it involves epithelial damage followed by immune-mediated inflammation and fibrosis during repair. Primary symptoms are dyspnea and cough. Unfortunately, bronchiolitis obliterans is often refractory, with no definitive cure. Symptomatic relief may be achieved through inhalers, antitussives, or oxygen therapy. Macrolides, systemic corticosteroids, and immunosuppressants may benefit some patients, but efficacy varies.

CAUSES

How does adenovirus pneumonia occur?

Currently, it is believed that adenovirus pneumonia is related to the adenovirus itself and the inflammatory response triggered by the virus in the body.
Adenovirus is the causative virus of the disease. Patients may also be co-infected with viruses other than adenovirus or develop secondary bacterial and fungal infections.

Adenovirus can cause severe pulmonary and systemic inflammatory reactions, which may progress to multiple organ failure [3].

Is adenovirus pneumonia contagious? How is it transmitted?

Adenovirus is contagious.

The incubation period for human adenovirus infection generally ranges from 2 to 21 days, with an average of 3 to 8 days. The period from the end of the incubation phase to the early stages of illness is when the virus is most contagious.

Both symptomatic patients and asymptomatic carriers can be sources of transmission.

Adenovirus is typically spread through the following routes:

1. Droplet transmission: The primary mode of respiratory adenovirus infection, such as when a patient coughs or sneezes.
2. Contact transmission: For example, touching surfaces or objects contaminated with adenovirus and then touching the mouth, nose, or eyes without washing hands.
3. Fecal-oral transmission: Digestive tract adenovirus infections can spread through the feces of infected individuals, such as during diaper changes. Additionally, adenovirus can be transmitted through water, such as swimming pool water contaminated with adenovirus, which may cause conjunctivitis [3].

Who is most susceptible to adenovirus pneumonia?

Adenovirus pneumonia most commonly occurs in children aged 6 months to 5 years, particularly those under 2 years old.

People of all ages can be infected with adenovirus. However, patients with chronic underlying conditions or weakened immune systems (e.g., organ or stem cell transplant recipients, HIV infection, primary immunodeficiency) are at higher risk of developing pneumonia and more likely to progress to severe pneumonia.

Adenovirus is highly contagious and can often cause outbreaks, primarily in enclosed, crowded, and humid environments such as military barracks, schools, childcare facilities, and hospitals [3].

DIAGNOSIS

When Should You Seek Immediate Medical Attention for Adenovirus Pneumonia?

Seek medical care promptly if any of the following symptoms occur:

• Children develop fever (temperature above 38°C), poor mental state, unusual irritability or clinginess, refusal to eat or drink, convulsions, or rashes. If pneumonia is suspected, seek medical attention immediately. Childhood pneumonia can be severe, especially without prompt treatment.
• Immunocompromised individuals (e.g., organ or stem cell transplant recipients, cancer patients, or those with HIV) experience fever, cough, or other symptoms.
• Symptoms worsen, including persistent high fever, prolonged cough, wheezing, or difficulty breathing.
• Extrapulmonary symptoms such as abdominal distension, diarrhea, nausea, vomiting, headache, irritability, or drowsiness.
• Critical conditions like hypoxia, cyanosis (bluish lips or fingertips), or shock.

How Is Adenovirus Pneumonia Diagnosed? What Tests Might Be Needed?

Adenovirus pneumonia is diagnosed based on epidemiological history, clinical and imaging findings, and adenovirus pathogen detection.

(1) Close contact history: Close contact with a confirmed adenovirus case within 8 days before fever onset.
(2) Symptoms and signs of adenovirus pneumonia: Fever, cough, sputum production, sore throat, difficulty breathing, fatigue, nausea, or loss of appetite.
(3) Imaging abnormalities: Chest X-ray or CT showing lung shadows, bronchiolitis, atelectasis, or emphysema. Like other viral pneumonias, adenovirus pneumonia may present as diffuse bilateral infiltrates, with severe cases progressing to "white lung."
(4) Pathogen confirmation: Positive adenovirus nucleic acid or antigen detection in respiratory specimens.

Possible diagnostic tests include:

• Chest X-ray or CT scan.
• Blood tests: Complete blood count, C-reactive protein, procalcitonin, liver/kidney function, cardiac enzymes, etc.
• Respiratory specimen collection (throat/nasal swabs or sputum): Adenovirus nucleic acid or antigen testing [3].

TREATMENT

How to Treat Adenovirus Pneumonia?

1. General Treatment: Similar to the general treatment for "viral pneumonia," including rest, increased water intake, ventilation, isolation, and disinfection.

2. Drug Therapy:
(1) Antiviral Drugs: Current antiviral medications, such as ribavirin, acyclovir, and ganciclovir, have uncertain efficacy against adenovirus and are not recommended. Cidofovir has been reported in case studies for adenovirus pneumonia in immunocompromised children, but its efficacy and safety remain unconfirmed.
(2) Immunomodulatory Therapy: Includes intravenous immunoglobulin and glucocorticoid treatment. Immunoglobulin is suitable for severe adenovirus pneumonia. Glucocorticoids may be used for patients with significant toxic symptoms, sepsis, or persistent wheezing due to bronchiolitis [3].

3. Others:

• Patients with high fever may undergo physical cooling (ice packs, cooling patches, etc.) or use antipyretics (e.g., acetaminophen, ibuprofen) for symptomatic relief.
• Patients with thick sputum may receive mucolytic agents like ambroxol or acetylcysteine for symptomatic treatment.
• Patients with wheezing may benefit from nebulization therapy.
• Patients with hypoxemia require oxygen therapy.
• Those with concurrent bacterial or fungal infections should receive appropriate antimicrobial therapy.
• Severe cases may require bronchoscopy to assess lesions, obtain bronchoalveolar lavage fluid for pathogen testing, remove necrotic tissue, or clear mucus plugs to improve airway patency.
• Mild cases are often self-limiting, and overtreatment should be avoided. Some children, especially infants and toddlers, may experience severe illness and require hospitalization.

DIET & LIFESTYLE

What should adenovirus pneumonia patients pay attention to in daily life?

Maintain good hygiene habits, wash hands frequently with soap and water, and wear a mask. Cover your mouth and nose when coughing or sneezing. Those with mild symptoms should rest in home isolation, minimize outings, and avoid public places. Avoid sharing cups or utensils with others and refrain from close contact. Ensure indoor ventilation.

Follow regular meal schedules, maintain adequate calorie, protein, and vitamin intake, drink plenty of water, and quit smoking and alcohol.

Get sufficient rest and avoid exhaustion or strenuous exercise. Seek immediate medical attention if severe symptoms such as persistent high fever, palpitations, or shortness of breath occur, and cooperate actively with treatment.

How to care for children with adenovirus pneumonia?

Keep the child as comfortable as possible, ensuring ample rest and fluid intake. For infants and toddlers, provide fluids in small, frequent amounts.

Regarding medication:

• Acetaminophen or ibuprofen may relieve pain and fever. The correct dosage depends on the child’s weight—consult a doctor for specifics.
• Avoid cough medicine for children, as it is often ineffective and may cause side effects.
• Do not give aspirin or aspirin-containing drugs to children under 18, as aspirin may trigger Reye’s syndrome, a serious condition.

If symptoms worsen or show no improvement after 2 days, seek hospital care immediately [5].

PREVENTION

Can adenovirus pneumonia be prevented? How to prevent it?

The best way to prevent it is to maintain hand hygiene. Wash hands frequently with soap, hand sanitizer, and water, or use alcohol-based hand sanitizer gels. Avoid touching the eyes, nose, and mouth with unclean hands, and avoid close contact with infected individuals.

Other methods to prevent the spread of infection include [6]:

• Wash hands with soap, hand sanitizer, and water after every diaper change for children.
• Clean sinks, countertops, and other surfaces with diluted disinfectant.
• Do not share towels, bedding, pajamas, or other personal items with others.
• Cover the mouth when sneezing or coughing.
• Quit smoking, maintain a healthy diet, exercise regularly, and adopt a healthy, active lifestyle.