Recurrent Respiratory Infections in Adults

Potential Causes and When to Be Concerned

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Recurrent respiratory infections are common in adults. Sometimes, however, they can be a sign of an underlying medical condition. This is especially true with serious respiratory infections such as recurrent pneumonia.

Increased levels of exposure may cause recurrent respiratory infections in some people. In other cases, structural problems such as a primary immunodeficiency disorder or lung cancer may be the cause.

Understand the "normal" incidence of respiratory infections, potential causes, and when it's important to talk to your healthcare provider. Regardless of the underlying cause, frequent respiratory infections can disrupt your life and potentially lead to complications if not addressed.

Risk Of Coronavirus. Sick Black Woman Coughing Hard At Home
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Normal Frequency of Respiratory Infections in Adults

Respiratory tract infections are less common in adults than children. In adults, a frequency of three to five infections per year is considered normal, but this depends on the type of infection and other factors.

Respiratory infections may be caused by viruses, bacteria, or fungi, and may involve the upper respiratory tract, the lower respiratory tract (bronchial tree), or both. Examples of upper respiratory infections include:

Examples of lower respiratory infections include:

While a few minor colds each year may be normal, other recurrent infections can signal a problem. For example, even two episodes of pneumonia in a year or three over an entire lifetime is considered abnormal.

Other indications that repeated infections are abnormal are discussed below, but one of the most important and seldom mentioned "symptoms" is your gut feeling. If your gut tells you something is amiss, it's important to talk to your healthcare provider regardless of how frequently you are having infections.

There aren't any studies that specifically describe the incidence of underlying conditions responsible for repeated infections. It is likely these conditions are underdiagnosed, however. For example, population studies suggest 1 in 1,200 adults has a significant underlying immunodeficiency disorder that can predispose them to repeated infections.

Importance of Evaluating Recurrent Respiratory Infections

Respiratory infections are often considered a nuisance, but it's very important to take them seriously when they recur. Have a thorough exam if there isn't a clear explanation as to why they are occurring. Sometimes this will only require a careful history and physical examination; other times a more intensive workup will be needed.

Repeated infections can cause complications (such as chronic lung disease). Additionally, a delay in diagnosis is the norm rather than the exception when a cause such as immunodeficiency or lung cancer is present. These conditions are most easily treated when caught early.

Signs and Symptoms

Many people are familiar with the typical signs and symptoms of respiratory infections. These may include:

  • Runny nose
  • Sinus pressure
  • Cough with or without phlegm
  • Sore throat and pain with swallowing
  • Fever
  • Chills
  • Sneezing
  • Wheezing
  • Hoarseness
  • Chest pain

Associated Signs and Symptoms

Additional symptoms may sometimes provide clues as to the underlying cause as well as the seriousness of recurrent infections. Signs and symptoms that raise concern include:

  • Coughing up blood: Coughing up even as little as a teaspoon of blood is considered a medical emergency.
  • Unintentional weight loss: Weight loss of 5 percent or more of body weight over a period of six to 12 months without trying is often due to a serious underlying cause.
  • Persistent cough despite treatment of infection
  • Shortness of breath
  • Persistent hoarseness
  • Chest pain
  • Rapid breathing (tachypnea)
  • Clubbing: Finger clubbing, a condition in which the ends of the fingers take on the appearance of an upside-down spoon, often indicates a serious underlying lung condition such as lung cancer.


Recurrent respiratory infections are not only a nuisance but can lead to further complications. Some of these include:

  • Bronchiectasis: A dilating of the airways that is a form of COPD, most commonly occurring as a result of recurrent respiratory infections in childhood
  • Stress incontinence: Respiratory symptoms from sneezing to coughing can lead to "accidents," especially in women who have had children
  • Loss of productivity at home/work/school
  • Financial complications due to the combination of lost work time and increased medical bills

Causes and Risk Factors

There are many potential causes of recurrent respiratory infections in adults. From a big-picture standpoint, these infections represent an imbalance between exposure to microorganisms (high microbial load) and the ability of the immune system to eliminate them.

Risk factors for repeated infections may include:

  • Increased exposure to infectious organisms, such as through living or working in a crowded environment or working in a daycare or school with young children
  • Smoking or secondhand smoke exposure
  • Winter months
  • Dry mucous membranes
  • Allergies to dust, pollen, molds, and more
  • Sleep deprivation
  • Lung diseases (such as bronchiectasis due to repeated respiratory infections in childhood)
  • Difficulty swallowing

When recurrent respiratory infections occur outside of obvious risk factors, the potential causes can be broken down into three main categories:

  • Anatomical problems
  • Secondary immunodeficiency
  • Primary immunodeficiency

Anatomic/structural abnormalities are most common with primary immunodeficiency disorders being least, yet immunodeficiency as a cause is underrecognized and underdiagnosed. Due to the importance of confirming or ruling out an underlying cause, we will look at each of these more closely.

Anatomic Problems

Anatomic or structural problems in the airways are the most common cause of otherwise unexplained recurrent respiratory infections in adults and include a wide range of conditions that may be congenital (present from birth) or acquired. Examples include:

Structural abnormalities: In the upper airways, abnormalities such as nasal polyps or a deviated septum can lead to chronic nasal/sinus infections. Abnormalities of the bronchi (the airways that leave the trachea and enter the lungs), such as congenital hypoplasia, can likewise lead to repeated lower respiratory tract infections.

Tumors: Unfortunately, tumors such as lung cancer are a far too common cause of recurrent respiratory infections in adults, and many people are treated for several lower respiratory tract infections before the diagnosis is made.

This is particularly true in never smokers, as lung cancer is not usually high on a healthcare provider's radar screen. That said, lung cancer is relatively common in lifelong never smokers, and the incidence is increasing. Other tumors may also lead to repeated infections.

Foreign bodies: Foreign bodies in the nasal passages are not common in adults (unlike children), but foreign bodies in the lower airways of adults sometimes lead to repeated infections. Unlike large foreign bodies that lead to choking and can be life-threatening, people often have no recollection of inhaling smaller foreign bodies.

Symptoms such as recurrent pneumonia may occur for months or years before the diagnosis is made. The exact frequency is unknown, but bronchial foreign bodies are found in 0.2 percent to 0.33 percent of all bronchoscopies. The most frequent finding is organic matter such as pieces of bones or seeds.

Aspiration: Aspiration (breathing contents from the mouth/esophagus/stomach into the lungs) is a relatively common cause of repeated infections. It is more common in people who have seizure disorders, other neurological conditions, or alcohol and/or drug abuse.

Lung diseases: Conditions such as bronchiectasis (dilating of the airways) are an important cause of repeated infections and may not be diagnosed until several infections have occurred. Other diseases that may lead to repeated infections include allergic bronchopulmonary aspergillosis and pulmonary vasculitis.

Cystic fibrosis: While cystic fibrosis is most often diagnosed in childhood, it is sometimes diagnosed in early adulthood or even later. Common symptoms include recurrent respiratory infections, and a prompt diagnosis is critical to improve survival.

Acid reflux: Gastroesophageal reflux disease (GERD) can lead to a chronic cough and repeated respiratory infections, but it is easily overlooked as a potential cause. Other abnormalities associated with infections may include Zenker's diverticulum (an outpouching in the region where the lower throat connects with the esophagus) and achalasia.

Alpha-1-antitrypsin deficiency (AAT): Alpha-1-antitrypsin deficiency is a relatively common hereditary condition affecting roughly 1 in 1,500 to 3,500 people of European ancestry. As a cause of COPD as well as liver disease in some people, it often presents with recurrent respiratory infections between the ages of 20 and 50.

While the condition cannot be cured, careful monitoring (and enzyme replacement therapy in those who have severe disease) may prevent complications such as severe COPD. AAT deficiency is also a risk factor for lung cancer, and being aware of the diagnosis could be important in lung cancer screening.

Secondary Immunodeficiency

Secondary immunodeficiency is a relatively common cause of recurrent respiratory infections in adults and refers to an immunodeficiency related to another medical condition. There are many conditions that could impact the immune system, including:

  • Infections such as HIV, Epstein-Barr virus (EBV), and cytomegalovirus (CMV)
  • Medications such as chemotherapy, chronic corticosteroid therapy, and immunosuppressive drugs
  • Cancers, especially blood-related cancers such as chronic lymphocytic leukemia and non-Hodgkin's lymphoma
  • Plasma cell dyscrasias
  • Nephrotic syndrome
  • Malabsorption

Primary Immunodeficiency

Primary immunodeficiency disorders are not common, but researchers are learning they are more common than previously thought and are thought to be underdiagnosed. Often considered a condition that presents in childhood, around 60% of immunodeficiency disorders remain undiagnosed until adulthood.

There are well over 200 different disorders that include antibody disorders, T cell disorders, combined B cell/T cell disorders, phagocyte disorders, complement disorders, and more. That said, a few in particular are more commonly discovered in adults who are experiencing repeated respiratory infections.

Selective IgA deficiency: Selective IgA deficiency is estimated to affect roughly one in 143 to one in 965 people (primarily Caucasians) and often goes undiagnosed. It is more commonly found in people who have celiac disease and/or allergies, and it often presents with either repeated respiratory or digestive tract symptoms.

There is no specific treatment for the disorder, but using antibiotics for infection and occasionally immunoglobulins are options. People who have IgA deficiency are also more likely to develop an autoimmune disease such as lupus.

Combined variable immune deficiency (CVID): CVID is characterized by low IgA levels, as with IgA deficiency, but also includes low IgG levels and sometimes low IgM levels. It is less common, affecting roughly one in 30,000 people, but the frequency can vary considerably with geography. It is often diagnosed in people in their 20s and 30s who present with repeated bacterial infections involving the lungs, sinuses, and ears.

Roughly 25% of people with CVID also have an autoimmune condition. Treatment is important to reduce chronic lung damage and includes regular immunoglobulin (gammaglobulin given either IV or IM) as well as the judicious use of antibiotics to treat infections. A high index of suspicion is important, as there is an average delay of four years between symptoms and the diagnosis.

Anti-polysaccharide antibody deficiency (SPAD): A 2017 small study postulated that specific anti-polysaccharide antibody deficiency may be linked with recurrent respiratory infections in the elderly, and it found an increased prevalence among those who experienced these infections. Rather than a congenital condition, they theorized it may be an acquired deficiency.

While the significance of this isn't yet clear, it is another reminder that primary immunodeficiency needs to be considered when other reasons for recurrent infections aren't apparent.

Others: There are many other primary immunodeficiency disorders, such as IgG subclass deficiencies and more, that may not be diagnosed until adulthood. Since the evaluation for these conditions is highly specialized, an immunology consult is usually recommended if there is any suspicion.


Diagnosing an underlying cause of recurrent respiratory infections requires being concerned in the first place—what healthcare providers call "having a high index of suspicion." This is important not just for healthcare providers but for patients as well.

Healthcare providers are human and don't have the advantage of living in your body 24/7. If you are concerned and your healthcare provider is not, consider getting a second opinion (or a third if needed). Symptoms are our body's way of telling us something is wrong.

When to Be Concerned

The American Academy of Allergy and Immunology provides a list of criteria that should raise suspicion of an underlying cause such as primary immunodeficiency disorder. Some of these related specifically to recurrent respiratory infections include:

  • Do you need antibiotic treatment more than two times each year?
  • Have you had pneumonia twice (at any time)?
  • Have you had any unusual or difficult-to-treat infections?
  • Have you required preventive antibiotics to reduce the number of infections you are having?
  • Have you required multiple courses of antibiotics (or intravenous antibiotics) to get rid of an infection?
  • Have you had more than three episodes of sinusitis in one year or do you have chronic sinusitis?
  • Have you had more than four ear infections in one year?
  • Have you had a very severe infection that began as a common infection?
  • Do you have a family history of primary immunodeficiency disorders? (Most people with these do not have a family history.)
  • Do you have enlarged lymph nodes (swollen glands) or an enlarged spleen?
  • Have you had any recurrent deep abscesses of your skin or other organs?
  • Do you have a history of any autoimmune diseases, including autoimmune thyroiditis?

Other questions that are important to ask include:

  • Do you or did you ever smoke?
  • Have you experienced any weight loss without trying?
  • Did you have repeated respiratory infections as a child?
  • Have you ever choked?


A workup for causes of recurrent infections should begin with a careful history of infections in the past, including the type and severity. Any conditions that were predisposing factors should also be noted. A thorough history should also look for other conditions that might suggest underlying immunodeficiency, such as delayed wound healing, dental problems, persistent warts, etc.

Physical Exam

A physical exam should evaluate the upper and lower respiratory passages checking for any abnormalities such as nasal polyps, abnormal breath sounds, scoliosis, clubbing, chest wall abnormalities, and any weight loss.


Imaging tests may be done depending on the location of the recurrent infections. This may include:

  • Sinus X-rays
  • Chest X-ray: It's important to note that a chest X-ray may be helpful if it reveals a disorder, but it cannot rule out several causes. For example, plain chest X-rays miss up to 25 percent of lung cancers.
  • Chest CT scan
  • Other tests such as MRI


Procedures may be helpful in looking for structural abnormalities in the respiratory tree.

  • Nasal endoscopy may be done to look for nasal polyps or a deviated septum
  • Bronchoscopy may be done to look for evidence of a foreign body or a tumor

Lab Testing

A number of blood tests may help narrow down potential causes, including:

  • Complete blood count (CBC) and differential looking for low levels of white blood cells, red blood cells, or platelets. A peripheral blood smear can also be helpful.
  • Metabolic panel
  • HIV testing
  • Sweat chloride (to screen for cystic fibrosis)
  • ANCA (anti-neutrophil cytoplastmic antibody) test to screen for Wegener's granulomatosis or microscopic polyangitis
  • Protein electrophoresis (looking for Bence Jones proteins and more)
  • Immunoglobulin levels: Testing for primary immunodeficiency disorders usually entails several steps, beginning with immunoglobulin levels. Further testing may be needed, such as antibody response investigations, complement studies, and more, and is often performed by an immunologist who specializes in immunodeficiency disorders.


Depending on the workup, further evaluation by other specialists may be needed such as ENT, pulmonary, immunology, and others.


The treatment of recurrent respiratory infections will depend on the underlying condition but must also address the infections at the time to minimize the risk of long-term damage.

Options for treatment may include treatment of a structural abnormality or tumor, immunoglobulin replacement therapy, preventive antibiotics, and more.

A Word From Verywell

The possible causes of recurrent respiratory infections are many and diverse, and it may feel overwhelming if you've been living with repeated infections. While we mentioned many potential options and tests, a careful visit with your healthcare provider can often help narrow down the potential causes and reduce your anxiety.

It's important to address the underlying causes in order to reduce the risk of damage to your airways (or to treat a treatable disorder as soon as possible), but also to maximize your quality of life. Repeated infections can cause havoc on your personal, social, and work lives, and tax your relationships.

Having a diagnosis, or at least knowing there is not an underlying cause, can sometimes reduce anxiety people aren't even aware is present.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."