The Flu – What You Need to Know
Viruses cause a variety of illnesses in humans ranging from mild upper respiratory infections (URI’s) to life-threatening pulmonary and extra-pulmonary diseases. Rhinoviruses, adenoviruses, respiratory syncytial virus (RSV), coronaviruses, and influenza are the most common viruses infecting the respiratory tract. Among these rhinoviruses, RSV and influenza viruses are common causes of wheezing in children. Recurrent infections with these viruses may play a role in the development of asthma.
Patients with asthma are more susceptible to contract infections with influenza virus. In addition, they are also more likely to develop serious complications from Influenza. In fact, more than 75% of acute flare-ups of asthma are triggered by infections from either influenza, RSV, or rhinovirus infections.
Influenza infection (i.e., flu) normally occurs in the United States between October and March, although the peak time for infection is between January and March. There are 3 strains of influenza viruses that cause human infections and one other that does not. The ones that cause human infections are known by the names influenza A, influenza B, and influenza C. Influenza D is not known to infect or cause illness in humans and primarily infects cattle.
Influenza A and B are typically associated with seasonal epidemics of disease, known as the flu season. Influenza A is the only influenza virus that has been associated with flu pandemics. There have been several flu pandemics during the 20th century, each with its own severity and outcome. For example, in 1918, the “Spanish flu”, a strain of H1N1 influenza A subtype H1N1, caused between 50 and 100 million deaths worldwide with a mortality rate of 2.5 to 3%. Most of the deaths occurred in adults between the ages of 20 and 40 years. In 1957, the “Asian flu” (influenza A subtype H2N2) caused between 1.5 and 2 million deaths and had a fatality rate of 0.67%. In 1968, the “Hong Kong flu” (influenza A subtype H3N2) has been estimated to have caused between 1 and 4 million deaths and had a mortality rate of less than 0.5%.
Influenza infection begins with invasion of the respiratory epithelium which serves as a site for both viral replication and the host’s immune response. Destruction of the normal airway tissue and a pro-inflammatory immune response are the primary causes of symptoms associated with influenza infection.
The immune response of the host causes many of the symptoms associated with viral respiratory infections and those associated with exacerbations of underlying asthma. Certain individuals seem to be at higher risk for developing infection in the lower airway. The risk of infection increases in children less than 6 months of age, individuals with second-hand smoke exposure, and in people with certain genetic markers. Allergic individuals are also more susceptible to infection due to an impaired immune response.
The classic symptoms of the flu may include:
- Runny nose
- Nasal congestion
- Sore throat
- Cough
- Fever/chills
- Achiness
- Vomiting or diarrhea
- Fatigue/Lethargy
Complications of the flu may include:
- Pneumonia
- Flare-ups of asthma symptoms
- Ear infections
- Inflammation of the heart muscle
- Inflammation of the brain
Treatment of the Flu:
Most cases of influenza are mild and the symptoms usually resolve in 7 to 10 days. Symptomatic relief of fevers, chills, and achiness can be achieved by over-the-counter medications such as acetaminophen (i.e., Tylenol). Antihistamines and decongestants may be utilized to help reduce the unwanted nasal symptoms. Inhaled medications such as albuterol (e.g., Proventil, Ventolin, ProAir) are given to help relieve wheezing, coughing, and/or shortness of breath. Rest and drinking plenty of fluids may accelerate the recovery process overall.
The indications for antiviral medications include patients that are at high risk of influenza-related complications including pregnant women, adults over 65 years of age, immune-compromised subjects, and those with chronic medical conditions such as asthma, chronic obstructive pulmonary disease (COPD), and diabetes. Antivirals should be used if an individual requires hospitalization, if the infection is severe or complicated, and during pregnancy (even in mild disease).
Antiviral treatment works best when begun soon after the flu illness begins. When treatment is started within 2 days of becoming sick with flu symptoms, antiviral drugs can lessen fever and flu symptoms and shorten the duration of illness. They also may reduce the risk of complications such as ear infections in children, respiratory complications requiring antibiotics, and hospitalization in adults.
- Oseltamivir (i.e., Tamiflu) is available as a pill or liquid suspension and is FDA approved for the early treatment of the flu in individuals 2 weeks of age and older who have had flu symptoms for 2 days or less.
- Zanamivir (i.e., Relenza) is a powder that is inhaled and approved for the early treatment of the flu in people 7 years of age and older. Note: Zanamivir is administered using an inhaler device and is not recommended for individuals with breathing problems such as asthma or COPD.
- Oseltamivir and zanamivir are given twice a day for 5 days.
- Baloxavir (i.e., Xofluza) is a pill given as a single dose by mouth and is approved for the early treatment of flu in individuals 12 years of age and older. Note: Baloxavir is not recommended for pregnant women, breastfeeding mothers, severely immunosuppressed individuals, hospitalized patients, or outpatients with complicated or progressive illness.
Prevention of the Flu:
Staying home and avoiding contact with others will reduce the risk of acquiring influenza infection.
Routine annual influenza vaccination (i.e., flu shot) is recommended for all persons 6 months of age and older. Many types of flu vaccines are licensed by the FDA this year with varying indications based on one’s age group and health status. Please click on the following CDC link for more information: cdc.gov/flu/prevent/keyfacts.htm
The board certified allergists at Black & Kletz Allergy located in the Washington, DC, Northern Virginia, and Maryland metropolitan area will readily answer any questions you have regarding the flu, asthma, and/or allergies. We have 3 offices with locations in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA. All of our offices offer on-site parking. In addition, the Washington, DC and McLean, VA offices are accessible by Metro. There is also a free shuttle that runs between our McLean, VA office and the Spring Hill metro station on the silver line. Kindly make an appointment by calling one of our 3 offices. Alternatively, you may click Request an Appointment and we will answer your inquiry within 24 hours by the next business day. Black & Kletz Allergy treats both children and adults and we are proud to serve the Washington, DC metro area residents for which we have done for more than 5 decades.