Why the Flu Is Dangerous for People With Asthma

Flu can trigger or worsen asthma and cause serious complications

Influenza (flu) is among the several potential triggers for asthma. Infection with a flu virus can exacerbate inflammation of the airways and lungs, not only triggering the symptoms of asthma but making them worse.

You are not more likely to get the flu just because you have asthma, but you are more likely to experience related complications—such as bronchitis and pneumonia—and require hospitalization as a result of infection.Even people with mild or well-controlled asthma are at a high risk of serious health problems from the flu.

Woman with the flu
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The Connection

Asthma is often the result of a strong response of the immune system to a substance in the lungs. Although there's no direct connection between contracting the flu and developing asthma, having viral respiratory infections and wheezing as a child is an overall risk factor for developing asthma or having it worsen.

People with asthma have chronically swollen and sensitive airways, and getting the flu can exacerbate the inflammation and increase mucus production. As the swelling increases, bronchoconstriction (tightening of air passages) can simultaneously occur, triggering an asthma attack and making breathing more difficult.

In addition, preliminary research examining lung samples suggests that the immune system response to flu is weaker in those with asthma than those without an existing lung condition. More research is needed to confirm this finding and to uncover whether it may be due to the asthma itself or immunosuppressive effects of common asthma medications, such as inhaled corticosteroids.

Symptoms

Asthma symptoms can occur at any age, but they often develop in childhood. There are four main symptoms of asthma:

Symptoms may occur daily or only every once in a while. It's also common for symptoms to occur or get worse in the evening. A chronic cough can be a sign of poor asthma control.

Unlike asthma, flu is contagious and caused by influenza viruses that can infect the nose, throat, and lungs. It can cause mild to severe illness, and sometimes can lead to complications and death.

Unlike a cold that comes on slowly, the flu typically has a sudden onset of symptoms, such as:

  • Fever
  • Chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headache
  • Fatigue

Some people may also have vomiting and diarrhea with the flu; these symptoms are more common in children than adults.

Anyone with the flu can develop a cough,which can be especially problematic in those with asthma because it can compound the cough they may already be experiencing due to their condition.

And while standard inflammation from the flu does not typically lead to shortness of breath or wheezing in most people, those with chronic lung conditions such as asthma or severe cases that requires emergency medical attention are exceptions.

In these individuals, the inflammatory response to the viral infection acts as a trigger for a sudden worsening of asthma symptoms.

Most people recover from the flu within a few days to two weeks, but people with asthma have an increased risk of developing sinus, ear, or lung infections.

Complications

The combination of the flu and asthma, including bronchoconstriction and excess mucus production, challenges the immune system and further compromises lung functioning that is already impaired. This can delay recovery and increase the risk of bronchitis or pneumonia, as well as hospitalization.

Asthma is the most common medical condition among children hospitalized with flu. A study published in 2011 in the journal Pediatrics found that 32% of children hospitalized for seasonal flu over a six-year period had asthma. Children with asthma also represented 44% of all pediatric hospitalizations for H1N1 virus during the 2009 pandemic.

People with moderate to severe asthma may also be at higher risk of getting very sick from COVID-19, which can affect the lungs and cause an asthma attack.

Aside from asthma, factors and conditions that can increase the risk of complications from flu include:

Warning Signs

If you or your child have the flu and your symptoms improve but then return and worsen, or you experience any of the following symptoms, seek emergency medical care:

  • Difficulty breathing/shortness of breath
  • Persistent pain or pressure in the chest or abdomen
  • Ribs pulling in with each breath
  • Persistent dizziness, confusion, inability to arouse
  • No urination
  • Severe muscle pain
  • Severe weakness or unsteadiness
  • Seizures
  • Bluish lips or face

Causes

The causes of asthma aren't fully understood, but it is believed that the condition stems from a combination of genetic predisposition and environmental factors.

You are at an increased risk of developing asthma or having asthma symptoms worsen if any of the following apply:

There are two main types of flu viruses that routinely circulate each year: influenza A and influenza B. Influenza A is the type that is responsible for some pandemic viruses, such as H1N1 virus.

Flu can happen at any time, but is mostly a concern during flu season, starting as early as October and ending as late as May. The timing coincides with months that have the most cold, dry air—a common asthma trigger.

Flu viruses can spread by droplets released when people who are infected cough, sneeze or talk.These droplets can land in the mouths or noses of people who are nearby. It may also spread when someone touches a surface that has flu droplets on it and then touches their own mouth or nose.

Those who have the flu are most contagious in the first three to four days after their illness begins, but they can infect others one day before symptoms develop and up to seven days after becoming sick.

Young children and those with weakened immune systems, which may include people with asthma, may be able to infect others for even longer periods of time.

Causes of Asthma
  • Non-contagious

  • Genetic predisposition (risk factor)

  • Environmental factors (risk factor)

Causes of Flu
  • Contagious virus

  • Close contact with infected individual

  • Touching contaminated surface

Diagnosis

If you have asthma symptoms, your doctor will ask about your personal and family medical history, do a physical exam, and may have you do a series of pulmonary function tests (PFTs). There may also be additional tests, such as chest or sinus X-rays.

PFTs can help confirm an asthma diagnosis, but they are also used to measure breathing in those already know to have the condition. They are often done before and after a bronchodilator medication is used to open the airways.

These lung function tests may include:

If you have flu symptoms, your doctor can run tests to check if you indeed are infected. There are rapid tests that can give results within 10 to 20 minutes; these involve a swab of your nose or throat. While useful, they are not as reliable as viral cultures in which a swab of the nose or throat or a saliva sample is sent to a laboratory for analysis. Typically it takes one to three days for results of a lab test for flu to be returned.Sometimes both types of tests are necessary for a definitive diagnosis.

Diagnosis of Asthma
  • Chronic symptoms

  • Consider personal and family history

  • Physical exam

  • Pulmonary function tests

Diagnosis of Flu
  • Sudden onset of symptoms

  • Physical exam

  • Positive flu test

Treatment

The overall treatment plan for asthma depends on the frequency and severity of symptoms, but it will include carrying short-acting beta-agonists (SABAs), known as rescue inhalers, that can address acute symptoms by widening airways quickly. A rescue inhaler may be all that's needed for mild asthma or exercise-induced asthma.

Your physician will also help you develop an asthma action plan for recognizing asthma triggers and knowing what steps to take based on symptoms.

Most people with asthma also are prescribed one or more long-term controller medications to reduce inflammation and prevent symptoms over time, among them inhaled corticosteroids. These first-line medications for asthma are the most effective for long-term control of persistent asthma—defined as asthma that flares from several times a week to up to multiple times a day.

In many cases. inhaled asthma medications are taken daily, although people with mild to moderate persistent asthma may not need to use an inhaler every day according to updated recommendations from the National Institutes of Health issued in December 2020. If you use an inhaler daily to control asthma, you should not make any changes to your management plan without talking to your doctor.

Adhering to your asthma action plan, having a rescue inhaler with you at all times, and taking all controller medications as prescribed is important, especially during flu season, since symptoms can occur suddenly at any time.

When Flu Strikes

If you have asthma and develop flu symptoms, call your doctor as soon as possible. Your doctor may test you to confirm the flu and then give you a prescription for a type of flu treatment known as an antiviral. Antivirals work by suppressing viral activity which, in turn, alleviates the inflammation that can worsen asthma symptoms.

Typically, antivirals only decrease flu symptoms by about one day, but they may reduce the risk of complications, such as respiratory complications requiring antibiotics, ear infections in children, and hospitalization in adults.

Depending on the flu strains in your community, your doctor may recommend one or a combination of the following antiviral drugs:

People with asthma should not use that antiviral drug Relenza (zanamivir) because there is a risk it may cause wheezing in people with lung conditions.

As a general rule, people with asthma who think they have the flu should consider antiviral treatment, ideally within 24 to 48 hours of the first appearance of symptoms. Although, there is still some potential benefits even if the antiviral is taken after two days from the start of symptoms.

Additionally, persons with asthma can opt for antiviral therapy if they have no symptoms but believe they were exposed to the virus. Called chemoprophylaxis, the therapy aims to avert infection before symptoms arise. It should be started no later than 48 hours after exposure and continue daily for 10 days to two weeks, depending on your doctor's recommendation.

Asthma Treatments
  • Fast-acting, short-term medications (rescue inhalers)

  • Long-term controller medications, such as inhaled corticosteroids

  • Asthma action plan

Flu Treatments
  • Antivirals

Prevention

Due to the high risk of serious flu complications, people with asthma should get the flu vaccine, unless there is a medical reason not to, such as a history of anaphylaxis (a serious allergic reaction) after a flu vaccine or Guillain-Barré syndrome.

Each annual vaccine aims to prevent the four strains of influenza predicted to predominate that year.

Vaccination is relatively quick with few complications. If you have asthma and are concerned about getting a flu vaccine, there are some things to keep in mind:

  • Some physicians recommend the flu shot instead of the nasal spray for children and adults because of a concern that the nasal spray may have the potential to trigger an asthma attack. (Although, studies suggest that neither the flu shot nor FluMist increase the risk of asthma exacerbations.)
  • While people with an egg allergy once were advised not to get a flu shot, this is no longer the case, regardless of the severity of the allergy. If in doubt, speak with your doctor.
  • The idea a flu shot can cause the flu is unfounded. The vaccines are made from materials that only resemble the virus and can't give anyone the flu. (Even with the live, weakened form of the virus in FluMist, the virus is scientifically unable to cause the flu.)

In addition to the flu shot, it is recommended that you get a pneumonia vaccination if you haven't done so yet.

And don't underestimate the benefits of simple cold and flu prevention strategies, such as frequently (and properly) washing your hands, not sharing personal items, eating well, getting plenty of sleep, and more.

A Word From Verywell

If you have asthma, it's important to avoid asthma triggers, take your asthma medications as recommended, promptly refill supplies, and make sure you have an updated asthma action plan. If your asthma symptoms worsen or are more frequent or if you get the flu, contact your physician promptly.

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  1. Veerapandian R, Snyder JD, Samarasinghe AE. Influenza in asthmatics: for better or for worse? Front Immunol. 2018;9:1843. doi:10.3389/fimmu.2018.01843

  2. Nicholas B, Dudley S, Tariq K, et al. Susceptibility to influenza virus infection of bronchial biopsies in asthmaJournal of Allergy and Clinical Immunology. 2017;140(1):309-312.e4. doi:10.1016/j.jaci.2016.12.964

  3. National Heart, Lung, and Blood Institute. Asthma. Updated May 21, 2020.

  4. Centers for Disease Control and Prevention. Flu symptoms & complications.

  5. Juhn YJ. Risks for infection in patients with asthma (or other atopic conditions): is asthma more than a chronic airway disease? J Allergy Clin Immunol. 2014;134(2):247-57. doi:10.1016/j.jaci.2014.04.024

  6. Dawood FS, Kamimoto L, D'mello TA, et al. Children with asthma hospitalized with seasonal or pandemic influenza, 2003-2009. Pediatrics. 2011;128(1):e27-32. doi:10.1542/peds.2010-3343

  7. Kudo M, Ishigatsubo Y, Aoki I. Pathology of asthma. Front Microbiol. 2013;4:263. doi:10.3389/fmicb.2013.00263

  8. Centers for Disease Control and Prevention. How flu spreads. August 27, 2018.

  9. Centers for Disease Control and Prevention. Overview of influenza testing methods. Updated August 31, 2020.

  10. National Heart, Lung, and Blood Institute. Guidelines for the diagnosis and management of asthma (EPR-3). Updated September 2012.

  11. Cloutier MM, Baptist AP, Blake KV, et al. 2020 focused updates to the asthma management guidelines: A report from the national asthma education and prevention program coordinating committee expert panel working group. Journal of Allergy and Clinical Immunology. 2020;146(6):1217-1270. doi:10.1016/j.jaci.2020.10.003

  12. Centers for Disease Control and Prevention. What you should know about flu antiviral drugs. Updated September 3, 2020.

  13. Centers for Disease Control and Prevention. Flu & people with asthma. Updated August 31, 2020.

  14. Chang K-H, Lyu R-K, Lin W-T, Huang Y-T, Lin H-S, Chang S-H. Gulllain-barre syndrome after trivalent influenza vaccination in adultsFrontiers in Neurology. 2019;10. doi:10.3389/fneur.2019.00768

  15. Vasileiou E, Sheikh A, Butler C. Effectiveness of Influenza Vaccines in Asthma: A Systematic Review and Meta-AnalysisClin Infect Dis. 2017;65(8):1388–1395. doi:10.1093/cid/cix524

  16. Grohskopf LA, Sokolow LZ, Broder KR, Walter EB, Fry AM, Jernigan DB. Prevention and control of seasonal influenza with vaccines: recommendations of the advisory committee on immunization practices-United States, 2018-19 influenza season. MMWR Recomm Rep. 2018;67(3):1-20. doi:10.15585/mmwr.rr6703a1

  17. Centers for Disease Control and Prevention. Misconceptions about seasonal flu and flu vaccines.