Weekly Health Update: H1N1 Swine Flu Update

Health Report:

H1N1 Swine Flu Update

"A critical weekly review of important new research findings for health-conscious readers..."

By, Robert A. Wascher, MD, FACS

Updated: 09/13/2009

The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author. Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.

H1N1 SWINE FLU UPDATE

Influenza is a viral disease that has vexed mankind, and other animals, for thousands of years. The earliest definitive recorded observation of influenza in humans is contained in the writings of the renowned ancient Greek physician, Hippocrates, nearly 2,500 years ago.

Various strains of the influenza virus cause regular seasonal epidemics, or global outbreaks, which arise primarily during the fall and winter months. Because of this seasonal cycle of flu epidemics, there are generally two separate influenza epidemics each year (one in the northern hemisphere and one in the southern hemisphere).

Periodically, “super epidemics” of influenza, called pandemics, occur, resulting in very large numbers of flu cases. Unlike the regular seasonal flu epidemics, which reliably occur every winter, influenza pandemics are often associated with especially contagious and severe strains of influenza virus, resulting in large numbers of flu-associated deaths, particularly in more vulnerable victims (i.e., the very young, the very old, and people with serious preexisting illnesses). The worst recorded influenza pandemic in recent times was the 1918 “Spanish flu pandemic,” which resulted in the death of millions of flu victims around the world. Estimates of the number of deaths associated with the 1918 flu pandemic vary widely, as many deaths associated with influenza during this pandemic, doubtless, included deaths due to causes other than influenza. Nonetheless, between 20 and 100 million people are thought to have succumbed to influenza between 1918 and 1919, which approaches the number of deaths associated the Black Death plague pandemic (1348-1350), one of the deadliest pandemics in recorded human history. While typical seasonal influenza epidemics result in several hundred thousand deaths, globally, each year, pandemic flu outbreaks are often associated with millions of deaths (although, as with seasonal flu outbreaks, the lethality of individual pandemic-associated influenza outbreaks varies from one pandemic to the next).

Annual seasonal outbreaks of influenza are characterized by dominant strains of common human flu viruses, which tend to change from one year to the next. Influenza pandemics, however, frequently arise following the migration of new or uncommon strains of influenza viruses from animals to humans, or from human influenza viruses that acquire additional genetic material from animal strains of flu viruses.

Generally speaking, influenza is transmitted in the same manner as with other common viral respiratory infections. Viral particles adherent to respiratory secretions are primarily spread by coughing and sneezing, although flu viruses can also be spread through direct physical contact with infected secretions present on other people or on contaminated surfaces. As influenza viruses also afflict both birds and mammals, infected secretions (including feces and urine) from animals can also transmit flu viruses.

The symptoms of influenza are well known to most of us, and typically include fever, chills, muscle aches (myalgias), fatigue, headache, coughing, sore throat, nasal congestion and drainage, loss of appetite and, less commonly, abdominal pain, nausea and vomiting. Altogether, an estimated 150 different viruses are known to cause respiratory infections and flu-like syndromes in humans. However, infection with true influenza viruses commonly leads to more severe bouts of illness than is seen with most non-influenza viral infections.

Each year, public health experts try to predict which strains of flu virus will most likely predominate during the following year’s flu season, and three or more strains of influenza virus are selected to be included in the following year’s influenza vaccination. Occasionally, these educated guesses turn out to be inaccurate, and the resulting flu vaccine may therefore be relatively ineffective in a given year. However, annual influenza vaccinations are generally credited with dramatically reducing the incidence and severity of flu outbreaks in heavily vaccinated populations. (Since different strains of influenza predominate every year, seasonal flu vaccines must be updated every single year.)

Although antibiotics are ineffective against viruses, including influenza, there are several antiviral agents that are available as treatment for severe cases of influenza infection, particularly in patients with other serious and chronic health conditions or risk factors. However, while these antiviral agents can reduce the severity and duration of infections with influenza viruses, they are not able to complete eradicate the flu virus, as antibiotics do with bacterial infections. Importantly, most antiviral medications have to be given very early in the course of influenza infection (typically, within the first 48 hours after the onset of symptoms) in order to be maximally effective. In some selected cases, physicians may also recommend the use of antiviral medications in very high-risk patients as a flu prevention measure.

In April of 2009, a new strain of influenza first appeared in rural areas of Mexico. Because this particular strain of flu virus contains genetic material found in strains of influenza that commonly infect pigs, this new H1N1 influenza virus quickly became known as the “swine flu.” By June of 2009, the World Health Organization had already declared the H1N1 swine flu virus to be a pandemic virus, based upon its very rapid spread throughout the world.

According to the Centers for Disease Control’s (CDC) latest weekly flu update, more than 98 percent of current active influenza infections in the United States are being caused by the H1N1 swine flu virus. While most public health authorities are predicting a surge in the incidence of H1N1 swine flu infections during the upcoming fall and winter months, it is very important to note that, based upon clinical data acquired since the initial outbreak of this strain of influenza in Mexico, the health effects of the swine flu virus appear to be very similar to those observed with typical seasonal influenza viral infections. Just as with typical seasonal influenza epidemics, approximately 70 percent H1N1 swine flu patients who require hospitalization, due to severe flu infections, have one or more of the following associated high-risk medical conditions: age less than 5 years or greater than 64 years, pregnancy, chronic lung disease (including asthma and emphysema), heart disease, kidney disease, certain blood disorders (including sickle cell anemia), diabetes, immune system suppression (including HIV infection), certain neurologic or muscular disorders, and morbid obesity. Additionally, it should be noted that children and teens who are taking aspirin are at increased risk of acquiring a life-threatening complication of influenza infection known as Reye’s syndrome. (Once again, these same risk factors apply to typical seasonal flu outbreaks, as well.)

At the present time, a vaccine against H1N1 swine flu is in production. Although the release date for this vaccine (which will be given in addition to the usual annual flu season vaccine) has not yet been announced, public health experts hope to have the new vaccine available at about the same time as for the annual flu season vaccine. Meanwhile, the CDC recommends several simple but important steps to reduce your risk of infection: (1) cover your nose and mouth with a tissue whenever you cough or sneeze; (2) wash your hands with soap and warm water frequently, especially after coughing or sneezing; (3) avoid touching your eyes, nose, or mouth with your fingers; and (4) stay home from school or work if you develop flu-like symptoms.

Finally, I want to stress, once again, that the available clinical evidence, thus far, suggests that the H1N1 swine flu behaves, basically, like the more typical seasonal flu viruses that occur each and every year throughout the world. Be sure to take prudent measures to reduce your risk of contracting or spreading the H1N1 influenza virus, as I have outlined above. If you believe that you, or someone in your family, might have contracted the flu, then please do not delay seeing your physician, especially if any high-risk health factors are also present. When the H1N1 and annual flu season influenza vaccines become available, please also make sure that you receive both of these vaccines promptly.

Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity

Dr. Wascher is an oncologic surgeon, a professor of surgery, a widely published author, and a Surgical Oncologist at the Kaiser Permanente healthcare system in Orange County, California