A Primer on Swine Flu


By Bryan Bledsoe

As you may be aware, an outbreak of a virulent form of influenza has developed in Mexico. Subsequently, cases are popping up all across the world. So, here’s a bit of information on swine flu.

What causes swine flu?

AP Photo/Alberto Saiz A medical staff member, left, leads two patients who are undergoing tests for the swine flu virus at a hospital in Valencia, Spain.

AP Photo/Alberto Saiz
A medical staff member, left, leads two patients who are undergoing tests for the swine flu virus at a hospital in Valencia, Spain.

Swine flu is a respiratory infection caused by the Influenza A virus. The influenza virus is a primitive virus that affects both mammals (including humans) and birds. The influenza viruses are RNA viruses; that is, their genetic material is RNA and not DNA.

What is a virus?

A virus is a microscopic object that is significantly smaller than a bacterium. In fact, viruses can only be seen with an electron microscope. Unlike bacteria, viruses do not contain the cellular machinery to reproduce. Instead, when they enter the cell of a host, they hijack the cell’s biochemical processes in order to replicate and produce millions of new viruses.

How many types of influenza are there?

Generally speaking, there are three major types of influenza virus: Influenza A, Influenza B and Influenza C. Influenza A viruses are the most virulent. They normally reside in aquatic birds, but have been known to “jump species,” as seen in the current outbreak. Specific Influenza A viruses can be identified by their serotype. These viruses have glycoproteins on their outer coat; the most common being hemagglutinin (HA) and neuraminidase (NA). The specific type of these glycoproteins can be used to identify the virus.

The current swine flu strain in question is H1N1 (H=hemagglutinin and N=neuraminidase). H1N1 is the same virus type that is thought to have caused the Spanish flu in 1918, which killed approximately 50-100 million people worldwide. The Avian Influenza virus (e.g. “bird flu”) has a serotype of H5N1.

What are the symptoms of swine flu?

Influenza A is primarily a respiratory virus. The strain of swine flu in Mexico appears to be more virulent than strains seen in the United States. Also, it tends to affect people between 25 and 45 years of age (influenza usually tends to affect older adults).

The signs and symptoms of swine flu include fever, cough, sore throat, body aches, headache, chills and fatigue. Some have reported diarrhea and vomiting associated with swine flu. In the past, severe illness (pneumonia and respiratory failure) and deaths have been reported with swine flu infection. Like seasonal flu, swine flu may cause a worsening of underlying chronic medical conditions.

How is swine flu spread?

Swine flu seems to spread like all Influenza A viruses — mainly person-to-person through coughing or sneezing from infected individuals. Some infections can occur by touching something with flu viruses on it and then touching the mouth or nose.

How can we slow spread of the virus?

Standard Precautions should be used. Frequent hand washing and use of a mask will help slow spread of the virus. Be sure to get plenty of sleep and maintain adequate nutrition.

Why won’t vaccines help?

There is not enough time to develop a vaccine, administer it, and wait for the person’s body to manufacture antibodies for the swine flu. Generally, flu vaccines are manufactured based upon the strain predicted to be a problem in the coming year. Lifelong immunity to Influenza A is virtually impossible because the virus, being so primitive, often replicates inefficiently or wrong (mutation) causing a novel new virus to develop, to which we do not have immunity.

Why are pigs involved?

Many of the influenza viruses can live in the tracheal tissue of pigs. Normally, swine influenza viruses don’t affect humans. However, when this current virus mutated, it “jumped species” and started infecting humans.

Is there a treatment?

Two antiviral drugs that inhibit neuraminidase, oseltamivir (Tamiflu) or zanamivir (Relenza), seem to help with swine flu. However, these drugs do not “cure” the flu, but tend to shorten its severity and course.

Should EMS people take Tamiflu or Relenza “just in case”?

Absolutely not! The CDC has specific guidelines for antiviral cases. Furthermore, these drugs will not prevent infection. Most importantly, Influenza A can develop resistance to antiviral agents quickly (this was seen in Avian Influenza outbreaks in Asia). So, if you get signs and symptoms of Influenza A, call your doctor.

For more information on the swine flu, see: http://www.cdc.gov/swineflu/.

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