Viral-Induced Asthma Diagnosis and Treatment

An estimated 40 percent of asthma exacerbations in adults are caused by a viral illness. This means that viruses, such as those that can cause the common cold or the flu, can lead to the development or worsening of asthma symptoms.

There are two ways viruses can trigger asthma symptoms:

• The first type of viral-induced asthma affects people who have no history of asthma, but who develop asthma symptoms (for example, a cough and wheezing) that begin after the viral illness.
• The second type of viral-induced asthma affects children and adults who already have persistent asthma. In other words, a viral illness worsens their asthma symptoms.

Several viruses can be blamed for triggering viral-induced asthma. Two common examples are the rhinovirus which causes the common cold, and influenza A which causes the flu. These viruses are most frequently found to cause bronchospasm (narrowing of the airways) and asthma. 

Another virus linked to asthma is the respiratory syncytial virus (RSV), which can cause respiratory infections in adults and children. In children, RSV can cause wheezing, particularly in children under two years of age, which can lead to hospitalization and even death in rare cases. This increase in airway sensitivity in children caused by RSV can sometimes linger long after the infection has been cleared.

In adults, RSV can cause wheezing and induce asthma symptoms in those who already have asthma, and in people with no history of asthma. The good news is that, unlike in children, the airway functioning in adults generally returns to normal much sooner, although it can still take a few months.

It's interesting to note that because these types of viral infections are more common during certain times of the year, viral-induced asthma cases tend to wax and wane with the seasons. For instance, rhinovirus has a peak season in late fall and influenza A peaks in late winter. RSV is most common in the winter months, with a peak season from January to February in the Northern Hemisphere.

When faced with a viral infection, the body triggers an inflammatory response to attack and defend. In upper respiratory infections, such as those that accompany a cold or flu, this response can cause airway swelling and trigger excessive mucus production.

Overall, it's unclear whether viruses attack the lower airway directly causing asthma symptoms, or whether inflammatory substances produced by infected cells in the upper airway then affect the lower airway.

Many people with persistent asthma can sense when their symptoms are worsening. However, it's a good idea for people with asthma to have a peak flow meter, which is a small device that you blow into to measure how well the lungs are functioning. This is because it's possible to have a significant decrease in peak flow numbers (less than 80 percent of normal) without having corresponding symptoms.

Anyone who notices a significant decrease in peak flow numbers, as compared to the usual personal levels recorded on a daily basis, should call their physician for advice about increasing asthma medications or seeking medical attention.

A physician should be able to diagnose viral-induced asthma in those who do not have a history of asthma by listening to the lungs. The doctor may also perform a nose and throat swab or take a sputum sample to detect whether a virus is present.

Many physicians have peak flow meters in their offices, which can be used to diagnose airway obstruction. If the person hasn't been monitoring his peak flow at home, the doctor can compare the patient's numbers to what would be predicted for someone of the same sex, age, and size.

At present, there are no effective medications to treat these common viruses and prevent the asthma attacks they may provoke. The best treatment is prevention, and the four effective ways to do this include: 

• Getting a flu shot every year
• Frequent hand washing with soap and water
• Limiting contact with people who have upper respiratory symptoms 
• Avoiding touching your eyes, nose, or mouth, which is how viruses are spread

Certain children in high-risk groups (for example, infants born before 35 weeks of gestation or infants with a chronic lung disease) are now given a preventive medication called Synagis (palivizumab). This medication is an antibody against RSV and has been shown to decrease the rate of hospitalizations associated with RSV.

Treatment for viral-induced asthma may include bronchodilators (medicines that open up the airways) for mild symptoms and steroids for more severe or prolonged attacks. Steroid inhalers have been shown to be effective for treating adults without asthma who have asthma-like symptoms after a viral infection. However, in the absence of any history of asthma, these symptoms generally go away in eight weeks or less. For severe viral-induced bronchospasm, oral steroids may sometimes be necessary, even in people without a history of asthma.

People with asthma are not more susceptible to viral infections than others, but they experience more lower airway effects from these infections. Getting a respiratory infection does not mean you will definitively have an asthma attack. Often, more than one trigger leads to an attack—like infection along with environmental exposures such as smoking or exposure to an allergen.

In the end, the best thing you can do is to try to optimize your overall health. Use tactics including eating nutritiously, exercising, seeing your primary care physician regularly, staying up to date on your vaccines, not smoking, and keeping your stress at bay.