Typical influenza disease is characterized by abrupt onset of fever, aching muscles, sore throat, and non-productive cough. Additional symptoms may include runny nose, headache, a burning sensation in the chest, eye pain and sensitivity to light. Typical influenza disease does not occur in every infected person. Someone who has been previously exposed to similar virus strains (through natural infection or vaccination) is less likely to develop serious clinical illness. Although many people think of influenza as the “flu” or just a common cold, it is really a specific and serious respiratory disease that can result in hospitalization and death.
The most frequent complication of influenza is bacterial pneumonia. Viral pneumonia is a less common complication but has a high fatality rate. Other complications include inflammation of the heart and worsening of pulmonary diseases (e.g., bronchitis). Reye’s syndrome is a complication that occurs almost exclusively in children—patients suffer from severe vomiting and confusion, which may progress to coma because of swelling of the brain. To decrease the chance of developing Reye’s syndrome, infants, children, and teenagers should not be given aspirin for fever reduction or pain relief.
Viruses cause influenza. There are two basic types, A and B, which can cause clinical illness in humans. Their genetic material differentiates them. Influenza A can cause moderate to severe illness in all age groups and infects humans and other animals. Influenza B usually causes milder disease and affects only humans, primarily children.
Subtypes of the type A influenza virus are identified by two antigens on the surface of the virus. These antigens can change, or mutate, over time. When a “shift” (major change) occurs, a new influenza virus is born and an epidemic is likely among the unprotected population. This happened when the novel H1N1 influenza virus appeared in March of 2009 and led to a major pandemic, lasting until the summer of 2010.
Influenza is transmitted from person to person by airborne droplets formed during coughing and sneezing. These droplets are inhaled or land on mucus membranes (lining of the nose or inside of the mouth or the conjunctiva). Influenza virus also can be transmitted orally. A person is most likely to pass on the virus during the period beginning one to two days before the onset of symptoms and ending four to five days after the onset. The incubation period of influenza is usually two days but can range from one to four days. For most people, the flu lasts only a few days, but some people get much, much sicker. Influenza is of particular concern in people with pre-existing heart and/or lung conditions, the elderly, children under 2 years of age and pregnant women.
Vaccination is the principal means of preventing influenza and its complications. Here are some additional steps that may help prevent the spread of respiratory illnesses like influenza:
The most effective way to avoid an infection with influenza is to receive the influenza vaccine annually. Influenza vaccines are safe and effective, and, contrary to a common misconception, they do not cause the flu. Because the influenza virus characteristically changes or mutates from year to year, each year it is necessary to prepare a new vaccine for protection from the new flu strains that are present that year. For this reason it is essential that everyone get immunized against the seasonal flu every year because last year’s vaccine may not be protective against this year’s virus strains. Also, the protection given by the vaccine can wane over time so that last year’s vaccination may not continue to be protective, particularly for individuals age 65 and older.
The latest update from the Advisory Committee on Immunization Practices (ACIP) of the CDC is now published. Here is why it matters. No flu season is the same. It is impossible to predict when the flu season will peak. We have lots of people to vaccinate—everyone 6 months and older—and there is a plethora of flu vaccine choices
There is big news about the types of flu vaccine available this year. Each year, ACIP updates its recommendations for seasonal influenza vaccination. Everyone 6 months of age or older needs vaccination every year. That hasn’t changed. For several decades the only type of influenza vaccine that was available was the “flu shot” that contained inactivated influenza virus (IIV). In the early 2000s a live attenuated influenza virus (LAIV) FluMist vaccine nasal spray was introduced and clinical studies at that time demonstrated that it was even more effective than the inactivated influenza vaccine. That nasal spray version of the vaccine became very popular, especially for children.
Careful monitoring studies of the efficacy of the various flu vaccines used during the two most recent flu seasons have shown that the live attenuated influenza vaccine (FluMist-quadrivalent) was much less effective in preventing influenza infection than it had been in earlier seasons or than the inactivated influenza vaccine (flu shot). The CDC held in depth discussions about what to do about this unexpected finding and after considering the consequences of allowing an influenza vaccine of uncertain potency to be made available, the CDC recommended that the LAIV (FluMist) not be included in the influenza vaccines recommended for the 2016-2017 season. However a trivalent LAIV will probably be available in Canada for 2016.
This year’s vaccine differs from the 2015-2016 vaccine with the inclusion of one new influenza A virus strain and a new influenza B virus strain. Selections of vaccines available this season include:
Because of the change in vaccine composition for 2016–2017, children aged 6 months through 8 years will need to have received 2 or more doses of influenza vaccine previously to require only 1 dose for the 2016–17 season.
For families with a member who has a primary immunodeficiency, we recommend that all members of the family should be given the inactivated (killed) vaccine. The vaccines usually become available in August or September. Studies have shown that immunization can still be effective when given well into February or March in some years, so it is important to ask for the vaccine even if the New Year has passed.
Why do we recommend that everyone be immunized? First, some patients with a primary immunodeficiency may benefit from the vaccine. Even if they do not, there is little down side to receiving the inactivated vaccine. Family members who are able to respond to the vaccine will be protected. Even if the patient with primary immunodeficiency does not respond to the immunization, he or she will benefit from having everyone else in the family protected from infection and not susceptible to bringing the virus home with them. We want to create a “protective cocoon” of immunized persons surrounding our patients so that they have less chance of being exposed. It would be a good strategy to encourage employers to provide influenza immunization programs at the place of work and schools to similarly encourage immunization of the student body to further extend this “cocoon.”
Individuals with primary immunodeficiency have the same risk of contracting flu as does the rest of the population. The same type of anti-viral medicine, i.e., Tamiflu or Relenza, which is effective for people with normal immune systems, would be effective for patients with primary immunodeficiency diseases who get influenza. Note that Ig replacement therapy may not protect against newly emerged strains of the influenza virus since the Ig contained in the currently available lots of IVIG or SCIG was obtained from donors several months ago, probably before the newer strains of influenza had circulated thru the donor population to result in antibody formation.
Influenza can be diagnosed rapidly by a test done in physician offices. If the test is positive, it is recommended that persons immediately begin anti-virus treatment. Speed is important in this situation since the antiviral medications are most effective if begun within 48 hours of the onset of the illness. It would be a good idea to discuss with your physician plans for dealing with influenza before you get sick so that you are prepared. If you do become ill, you should contact your doctor immediately about initiating treatment. However, it would be wise to contact your physician first, before going to their office, an urgent care facility or emergency room.
During the flu season, you may want to stay away from crowded public places, such as shopping malls, if you are concerned about exposure. Most people can get information from the national media and from their physicians on other ways to prevent exposure, as well as when to use additional precautionary measures.
There is no single recommendation that is applicable to every situation. Some medical advisors recommend that unless influenza is in their classroom children with primary immunodeficiency diseases should go to school. If there is a known direct contact with secretions from a flu-affected child or adult by the individual with primary immunodeficiency, some medical advisors suggest that the patient should go on Tamiflu once a day for 10 days. If the individual with primary immunodeficiency disease develops symptoms of influenza, that person should be treated with Tamiflu twice a day for 5 days. Relenza could also be used as the anti-viral treatment. The same treatment recommendations should apply to adults with Common Variable Immune Deficiency (CVID) or other primary immunodeficiency diseases. If you have any questions, please contact your specialist.
Revised September 2016