Influenza

January 9, 2000

Charles Booras M.D.

by Charles H. Booras, MD


In my medical practice, it’s common for people to refer to almost any respiratory illness as a “flu bug”. Most of the time, what they really have is a viral upper respiratory infection (a “cold”).

Infection with the real influenza virus is a much worse and even potentially serious infection that ranks as the top predator in the food chain of respiratory illnesses. Many “colds” can beat us up a bit, but influenza is more like going a few rounds with a heavyweight boxer. It’s much more brutal and takes quite a bit longer to get over.

What follows is a comprehensive overview of the illness, it’s treatment, and prevention. Please see the companion articles on The Influenza Vaccine, and The 1999-2000 Flu Vaccine Recommendations from the Advisory Committee on Immunization Practices (ACIP).

What is it?

Influenza (commonly called "the flu") is an acute, contagious, respiratory tract infection, which is caused by one of the influenza viruses (A, B, or C). Outbreaks of influenza happen nearly every winter, with varying severity. Influenza viruses are highly contagious and pass very easily from person to person through talking, coughing, sneezing and even shaking hands. The most difficult aspect of limiting the spread of this infection is that we are contagious for 1-2 days before we even begin to feel sick! Once someone with the flu passes the virus to someone who is well, it usually takes about 2 to 3 days for flu symptoms to start.

Influenza can strike large numbers of people, even entire populations, who have inadequate immune protection especially against a newly mutated virus. In an average year, influenza causes between 10,000 and 40,000 deaths, and is responsible for 50,000 to 300,000 hospitalizations in the U.S.

During this century, worldwide flu epidemics occurred in the following years: 1918-1919 (the "Spanish flu"), caused 20 million deaths worldwide, with 500,000 deaths in the United States; 1957-1958 (the "Asian flu"), caused 70,000 deaths in the US; and 1968- 1969 (the "Hong Kong flu”), caused 34,000 deaths in the US.

Most outbreaks occur between October and May, with peak intensity from late December through early March. Types A and B influenza viruses are responsible for epidemics that occur almost every winter and are also associated with hospitalization and death. Type C influenza does not cause epidemics, and it usually only produces a mild infection.

Over time, influenza viruses constantly change by mutation (a change in their viral genetic material). Mutations cause subtle alterations in the influenza virus that allow it to evade the human body's immune defenses formed from previous influenza encounters. This helps to explain why individuals are susceptible to recurring bouts of influenza throughout life. 

Symptoms

Depending on the type of flu that is active in a given year and a person's immunity, symptoms can be mild to severe. Onset of the disease is so strong and sudden that most people can remember the exact hour they became ill. The severity of influenza symptoms depends on the type of influenza virus, and the age and health of the patient. On average, the worst symptoms last 4 to 5 days, but full recovery can take several weeks. As long as the patient displays symptoms of influenza, he or she is considered to be contagious - capable of spreading the influenza infection to other persons. 

If complications develop, a "simple" case of the flu can escalate to pneumonia. Flu complications can be life threatening in the weak or infirm. Although the influenza virus primarily affects the respiratory system, it may also impact the musculoskeletal, nervous, and gastrointestinal systems. Consequently, a person with influenza may experience any or all of the following symptoms:

  • Chills
  • Moderate to high fever (101° F to 103° F)
  • Sore throat
  • Runny nose
  • Muscle aches
  • Headaches
  • Fatigue
  • Cough
  • Diarrhea
  • Dizziness

 When to see your doctor

If you think that you are "coming down with the flu," see your doctor as soon symptoms appear. A doctor's visit is most beneficial within the first 48 hours of an influenza infection, to allow prescribed antiviral medications to work most effectively.  

Also, seek medical attention promptly in the following situations: your fever or cough worsens; you are coughing up blood or thick, foul-smelling mucus; you have chest pain or shortness of breath; you develop an earache; or your pain is not controllable with over-the-counter medications.

Treatment

Over-the-counter: To ease flu symptoms, doctors recommend bed rest; drinking plenty of clear fluids (at least 2-3 quarts daily); and taking over-the-counter pain medicines, cough syrups, and nasal decongestants.

Precription Medicines: Two older prescription antiviral drugs, rimantadine (Flumadine®) and amantadine (Symmetrel®) are available to stop the influenza A virus from replicating (multiplying) in the body. These medications can lessen the severity and duration of influenza A only. They can also help prevent family members from contracting the illness. These medications are similar enough to list them together as far as the mechanism of action, dosage, and side effects.

Both are used to prevent or treat influenza type A infections. Flumadine® interferes with the activity of the viruses genetic material, blocking an essential step in the the process of viral replication. For Symmetrel®, the exact mechanism of action is unknown, though it appears to prevent the influenza A virus from penetrating and entering healthy cells.

They may be given alone or along with flu shots. They will not work for colds, other types of flu, or other virus infections.

Each medicine is best taken before exposure, or as soon as possible after exposure, to people who have the flu. If you already have the flu, continue taking the medicine for the full time of treatment even if you begin to feel better after a few days. This will help to clear up your infection completely. If you stop taking this medicine too soon, your symptoms may return. This medicine should be taken for at least 5 to 7 days. Take it on an empty stomach at least 1 hour before or 2 hours after a meal.

For the prevention or treatment of flu the dosage for both medications is:

  • Elderly adults—100 milligrams (mg) once a day.
  • Adults and children 10 years of age and older—100 mg two times a day or 200 mg once a day.

These medications may cause some people to become dizzy or confused, or to have trouble concentrating. Less common side effects can include; Difficulty in concentrating; dizziness; dryness of mouth; headache; loss of appetite; nausea; nervousness; stomach pain; trouble in sleeping; unusual tiredness; or vomiting.

The effects of Symmetrel® can be altered by amphetamines, diet pills, asthma and cold medicines, methylphenidate, nabilone, and pemoline. Anticholinergic drugs can increase the side effects of amantadine.


Two new drugs were recently approved by the Food and Drug Administration (FDA) to combat both influenza A and B. Treatment can lessen the length of time it takes to recover from the flu by about one day. What that can mean is one less day of school or work lost. To be effective, each of the flu-fighting drugs must be started within two days of the onset of symptoms.

Tamiflu® (oseltamivir phosphate), which comes in tablet form, is approved for use in patients older than age 18. The FDA on Oct. 27, 1999, approved Tamiflu for the treatment of uncomplicated influenza in adults whose flu symptoms have not lasted more than two days. This product is approved to treat Type A and B influenza; however, the majority of patients included in the studies were infected with type A, the most common in the U.S.

The most frequently reported side effects of Tamiflu were nausea, vomiting, bronchitis, trouble sleeping and dizziness.

This drug has not been shown to be effective to prevent the flu or to decrease the risk of transmitting the virus to others.

It is not approved for use in children under the age of 18. The recommended dose of Tamilflu is one 75mg capsule taken twice daily for 5 days. It and may be taken with or without food. Tamiflu will be marketed by Roche Laboratories Inc.

Relenza® (Zanamivir), which comes as a powder that is inhaled into the lungs, is for use in adults and in children aged 12 and older. Zanamivir is believed to interact with the gene for an essential viral enzyme, neuraminidase. The resulting inhibition of its synthesis may block the release of the virus.

The dosage for adults and teenagers is 2 inhalations (one 5-mg blister per inhalation) every 12 hours for 5 days. On the first day of treatment, however, 2 doses should be taken whenever possible provided there is at least 2 hours between doses. On subsequent days, follow the above dosage schedule. 

Because these drugs are available only by prescription, it's important that you see or contact your doctor immediately if flu symptoms, such as fever, body ache and sore throat, appear during a known influenza outbreak.

Prevention

During epidemics, physicians can prescribe he above anti-viral medications to high-risk individuals which will lessen their chance of acquiring influenza. You can also reduce your chances of getting influenza by practicing good hygiene, especially frequent hand washing. Hand washing helps to remove the influenza virus, which is often spread through direct contact (kissing, shaking hands, eating/drinking after one another), or by touching contaminated surfaces. The virus can live on some surfaces for hours or even days.

During the annual epidemic, about 20 to 30 percent of Americans will be infected, and about 20,000, mostly elderly, will die. Although the elderly and infirm have long been cautioned to prepare for the annual epidemic by getting a flu shot, it now appears that even relatively young and healthy adults stand to benefit from immunization The influenza vaccine is regarded as the top weapon against influenza, and it is 70%- 90% effective in helping healthy persons under age 65 avoid, or lessen the severity of, "the flu." Because timing of the vaccine heightens its effectiveness, doctors advise people to get flu vaccines between October and November, the start of the flu season.

In mid-September 1999, the American Academy of Family Physicians (AAFP) announced it was lowering its recommended age for flu vaccination from 65 years old to 50. In doing so, the AAFP is going beyond the guidelines laid down by the Advisory Committee on Immunization Practices (ACIP), the most widely accepted national authority on immunization.

In a study of health care workers younger than age 50 it was found that the flu vaccine could significantly reduce the number of sick days. For every 100 health care workers vaccinated, a total of 11 sick days were prevented, which translates into increased productivity and a reduced need for replacement workers. Other studies of healthy workers have shown that the flu vaccine reduces the amount of respiratory illnesses by 25 percent and cuts absenteeism in half.

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