Worldwide, annual influenza epidemics result in an estimated 3–5 million cases of severe illness and 250,000-500,000 deaths every year. Globally, an estimated 300 million people suffer from asthma. Asthma prevalence varies widely between different countries ranging between 1 and 18%.
People with asthma are at higher risk of developing serious flu complications, even if their asthma is mild or their symptoms are well-controlled by medication.
Asthma and the 2009 Influenza A (H1N1) Pandemic
Previous studies have shown that asthma is common among patients hospitalized with influenza. Asthma and influenza are two pathologic conditions of the respiratory tract that affect millions worldwide. Influenza virus of the 2009 pandemic was highly transmissible and caused severe respiratory disease in young and middle-aged inpiduals. Asthma was discovered to be an underlying co-morbidity that led to hospitalizations during this influenza pandemic.
Several reports from different countries identified asthma as the single most common comorbid condition among hospitalized inpiduals with H1N1 infection, with rates of asthma ranging from 10% to 32%. However, these studies did not include concurrent control groups for their investigations. Asthma was an undisputed risk factor associated with hospitalization affecting 10–20% of the hospitalized populations worldwide, and approximately a quarter of the hospitalized patients in the United States during the Swine Flu pandemic.
How can Flu Trigger Asthma Attacks?
Asthma is a common chronic inflammatory disease that affects the lungs, causing repeated episodes of wheezing, chest tightness, and shortness of breath. Influenza is a contagious respiratory illness caused by a virus. It is spread by respiratory droplets from close contact with infected persons or contact with contaminated surfaces or objects.
Colds and flu are the top triggers for people with asthma, with 75% of people with asthma saying their symptoms get worse when they have a cold or the flu. Having a cold or the flu alongside asthma also puts you at risk of an asthma attack that could be life-threatening.
When you have a cold or the flu, your airways become more inflamed and you produce more mucus. This means there’s less room for the air to get through which can make it harder to breathe. This can then trigger your asthma symptoms. In normal airways, the steady-state environment of mucus production, mucociliary clearance (MCC), and innate immune defenses play key roles in protecting the respiratory system from inhaling environmental harmful substances including viruses. However, in the infected airways, excessively secreted pathological mucus may block MCC and airflow, resulting in airway obstruction and even respiratory distress. Mucus hypersecretion, accumulation, and increased mucus viscosity largely influence disease development and prognosis.
People with asthma can develop swollen and sensitive airways, and flu can cause further inflammation of the airways and lungs. Flu also can lead to pneumonia and other acute respiratory diseases. In fact, adults and children with asthma are more likely to develop pneumonia after getting sick with flu than people who do not have asthma. 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.
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.
Children
Influenza viruses are important causes of respiratory tract illness in infants and children. Influenza-related deaths in children are infrequent but influenza-attributable hospitalization rates in young children or high-risk children are quite high. Previous studies found high incidences of admission among children less than 2 years old. The spectrum of influenza infection in children ranges from subclinical illness to complicated disease involving multiple organs, and pneumonia is one of the common presentations.
Asthma represents the most common chronic disease of childhood. Respiratory tract infections represent the most common trigger for acute asthma exacerbations, accounting for 60% of adult and up to 80% during childhood. Asthma is the most common medical condition among children hospitalized with flu and one of the more common medical conditions among adults hospitalized with flu.
Asthma and Flu Vaccines
Generally speaking, the flu vaccine is a potent defense against influenza infections. There is good scientific evidence that flu vaccines can help people with asthma. A 2017 meta-analysis found that people with asthma are less likely to get the flu after receiving a flu vaccine. The vaccine also seems to reduce the chances that people with asthma will experience an attack or flare-up. A 2020 study found similar results, stating that flu vaccines have great potential for reducing asthma attacks related to flu. As well as taking the flu vaccine, people with asthma can take preventive measures to reduce their chances of infection with the influenza virus.
Tips to reduce the Risk of Catching the Flu
Wash your hands frequently to reduce the risk of catching a cold or the flu. Take care to avoid sharing towels, cups or other household items with someone who may have a cold. Try not to touch your eyes or nose. Look after yourself: get plenty of sleep and try to reduce your stress levels.
Everyone 6 months of age and older should get a flu vaccine every season, especially people at high risk.A flu shot is the best way to reduce your chances of getting the flu and spreading it to others. Vaccinating your child also protects people around them (like grandparents, babies or anyone with long-term health problems) who are more vulnerable to flu. Although the flu shot might not protect against every flu strain, the vaccination can help lessen the severity of the flu and keep asthma patients from potentially getting sicker.
The vaccine is advised for all children 6 months and older. But for some children, it’s more critical for them to get a flu shot. The flu shot should be given to any child who has any of these: a long-term heart or lung condition, an endocrine disorder such as diabetes, a kidney or liver disorder, weak immune system from HIV/AIDS or long-term steroids and a blood disorder such as sickle cell disease. A flu shot should also be given to a child who has a family member with a chronic health condition, a child or teen taking aspirin as long-term therapy and a child with parents or caregivers at high risk of complications from the flu.
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