What Is Viral-Induced Asthma?

Viral-induced asthma is the onset of an asthma attack due to a respiratory tract infection. This includes viruses associated with the common cold and flu. It is estimated that no less than 50% of all acute asthma attacks are triggered by a respiratory virus. As opposed to poorly controlled asthma—in which attacks occur due to inadequate drug treatment or adherence)—viral-induced asthma can occur even in people with excellent asthma control.

At present, there are no drugs known to reduce the frequency or severity of viral-induced asthma. The prevention of respiratory tract infections remains the best way to reduce your personal risk.

Viral-Induced Asthma Symptoms

Viral-induced asthma can prompt a new onset of symptoms in adulthood (adult-onset asthma). In many cases, a person will have had asthma in early childhood that disappeared only to reappear later in life.

It can also cause asthma exacerbations—attacks that occur in children and adults already diagnosed with asthma, including those with well-controlled disease.

Regardless, the symptoms of viral-induced asthma are not dissimilar to other types of asthma, but they can often be more severe due to the co-occurring infection. This is especially true in people who smoke or have poorly controlled asthma.

Common symptoms of viral-induced asthma include:

• Wheezing
• Coughing
• Chest tightness
• Shortness of breath
• Fever
• Chills
• Fatigue
• Nasal congestion
• Headache
• Sinus pain
• Runny nose
• Sneezing
• Loss of appetite

Adult-onset cases are especially troublesome as they are likely to be more persistent and harder to control, with a more rapid decline in lung function. This can increase a person's vulnerability to infection, including severe recurrent respiratory infections.

People who routinely use a corticosteroid inhaler to control asthma are also more likely to develop pneumonia following a bout of viral-induced asthma due to the immunosuppressive properties of the drug.

Likewise, severe or prolonged lower respiratory infections occurring within the lungs can make it more difficult to manage asthma, leading to a potentially severe asthma attack and a concerning cycle of illness.

Causes

Viral-induced asthma is linked to certain respiratory viruses. Among those associated with acute exacerbations or the new onset of disease are:

• Rhinoviruses
• Influenza viruses, especially influenza A
• Respiratory syncytial virus (RSV)
• Parainfluenza viruses
• Adenoviruses
• Coronaviruses
• Pneumonia viruses
• Human bocavirus
• Enterovirus 68

Of these, rhinoviruses account for 60% to 70% of all viral-induced asthma cases, with the majority of remaining cases linked to influenza viruses and RSV. However, it is unclear how these different viral infections trigger asthma.

Most scientists agree that there is not a simple cause-and-effect relationship. What follows are a few hypotheses as to why viral-induced asthma occurs.

Early Respiratory Infections

Infants with RSV infections during the first six months of life—when the immune system is still developing—are more likely to experience asthma later in life.

This suggests that early alterations of the immune response may cause an immune overreaction later in life when exposed to similar respiratory viruses.

On the flip side, a maternal history of asthma appears to increase the risk of severe lower respiratory tract infections in infants and babies.

Lower Respiratory Tract Involvement

Asthma is characterized by hyper-responsiveness of the airways of the lower respiratory tract.

With adult-onset asthma, a lower respiratory tract infection appears the most common risk factor for a first attack. This is likely because lower respiratory infections cause greater immune activation and airway inflammation.

Still, it is unclear how an upper respiratory infection caused by a rhinovirus, for example, can induce hyper-responsiveness in the lower respiratory tract.

Allergy-Induced Inflammation

The risk of viral-induced asthma appears closely linked to chronic allergies, including allergic rhinosinusitis. Some scientists believe that the degree of chronic allergic inflammation in the airways is predictive of a person's risk of viral-induced allergies.

Diagnosis

Viral-induced asthma is often recognized by the development of classic asthma symptoms (bronchoconstriction accompanied by bronchospasms) in tandem with classic respiratory infection symptoms.

Another tell-tale sign is the sudden appearance of symptoms in people who have otherwise had excellent asthma control.

(If this is your first attack or you have not been previously diagnosed, your doctor will focus on treating the acute symptoms and refer you to a pulmonologist for a larger battery of tests to confirm that asthma is involved.)

People with viral-induced asthma will typically demonstrate a significant reduction of lung function when tested with spirometry and other pulmonary function tests (PFTs). There should also be a notable drop in the peak expiratory flow rate (PEFR) since respiratory infections can cause PEFR declines in both asthmatic and non-asthmatic people.

A chest X-ray may also be ordered if pneumonia is suspected, though this imaging is otherwise of limited value in diagnosing or characterizing asthma. A pulse oximeter will be used to measure blood oxygen levels as well.

Treatment

There are no specific treatments for viral-induced asthma other than what is commonly used to treat asthma exacerbations.

Among the treatments commonly prescribed to treat acute asthma attacks:

• Inhaled bronchodilators, including beta-2 agonists and anticholinergics, are the mainstay of asthma treatment in the emergency departments. Short-acting beta-agonist (SABAs), also known as rescue inhalers, provide rapid dilation of the airways. Anticholinergics like ipratropium and tiotropium have similar actions.
• Corticosteroids, also known as steroids, can be delivered by an inhaler, taken by mouth, or infused intravenously (into a vein). What's best depends on the severity of your symptoms.
• Antivirals can shorten the course and severity of influenza and RSV. Drugs like Tamiflu (oseltamivir) may improve outcomes in people with influenza if taken with 48 hours of the appearance of symptoms. Virazole (ribavirin) is an inhaled powder used to treat severe RSV infections.
• Epinephrine, also known as adrenaline, is delivered by injection during a medical emergency to quickly dilate blood vessels and open airways, thereby reducing blood pressure and improving breathing.
• Antibiotics may be prescribed to treat secondary infections, like bacterial pneumonia, that can occur in severe or prolonged infections.
• Oxygen therapy may be needed if there is hypoxia (low blood oxygen) or severe pneumonia.

Once your asthma is under control, your doctor will discuss treatment options to ensure better long-term management of your symptoms.

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Prevention

At present, there are no effective medications to prevent viral-induced asthma. Even if you take your asthma medications without fail and haven't had an attack in years, a viral-induced exacerbation can still occur.

Until effective drug interventions are found, the best form of treatment is prevention. Among the recommendations:

• Get a flu shot every year.
• Wash your hands frequently with soap and water.
• Avoid people with colds, flu, or other respiratory infections.
• Avoid touching your eyes, nose, or mouth.

Children in high-risk groups, including preterm babies and infants with chronic lung disease, are now given a preventive monoclonal antibody called Synagis (palivizumab) that may provide modest protection against RSV.

Scientists are exploring other medications that may one day protect against viral-induced exacerbations. These include inhaled interferon-beta which appears to enhance the body's response to certain respiratory infections. Research to date has been conflicted, although people with severe asthma appear to benefit.

A Word From Verywell

People with persistent asthma are not only susceptible to respiratory infections, but they tend to experience more severe symptoms if one occurs. With that said, getting a respiratory infection does not mean you will have an asthma attack. Often, more than one trigger will be involved, such as a respiratory infection in someone who smokes.

In the end, the best thing you can do to avoid viral-induced asthma is to optimize your health. Eating nutritiously, exercising, seeing your primary care physician regularly, staying up-to-date on your vaccines, and quitting cigarettes can go along way to avoiding illness or reducing the severity of a cold or flu infection, if one develops.