A swine flu H1N1 epidemic began in the U.S. in spring 2009, with thousands of cases reported worldwide. While the disease was mild for most people, there were concerns that it could become a pandemic which induced panic and fear in many people throughout the world.
The swine influenza virus occurs naturally in pigs, causing a respiratory disease much like flu in humans. Though historically rare, transmission of the Influenza A virus from infected pigs to humans has occurred sporadically. Additionally, once the swine flu has been transmitted to the human population, certain changes in the virus can lead to easy transmission between humans. One example of this was the pandemic Spanish Flu of 1918.
Name: Swine Influenza A
Type of Microbe: RNA Virus
How it spreads: Similar to the seasonal flu, via aerosolized droplets (such as sneezes or coughs), saliva and nasal secretions.
How it causes disease: Swine flu and seasonal human flu are nearly identical in the way the viruses cause disease and death. The virus attaches and enters into cells in the respiratory tract (nose, throat, and lungs), but is pretty much limited to those tissues. The virus is toxic to the respiratory tract cells and causes the immune system to respond with an influx of white blood cells and immune molecules known as cytokines. The influx of white blood cells results in some blocking of the airways, as well as damage to the lungs.
Cytokine activity within the respiratory tract results in inflammation, resulting in symptoms associated with flu: fever, chills, exhaustion, loss of appetite, and cough, as well as other respiratory symptoms.
Who’s at risk? People who are in contact with those who are infected, or virus-contaminated objects and surfaces.
Symptoms: Swine flu symptoms are predominantly the same as seasonal influenza, including fever, cough, sore throat, and muscle aches. In severe cases of untreated swine flu, the infection can lead to pneumonia, either from the infection itself or from secondary bacterial infections. Pneumonia is the leading cause of influenza-related deaths.
Diagnosis: To diagnose swine flu, a swab is collected from the nose or throat and sent for laboratory diagnosis. Lab diagnostic testing may include measuring specific viral proteins or growing the virus. To diagnose late disease, blood samples may be collected and measured for your body’s antibody response to the virus.
Prognosis: Prognosis depends on the strain of virus. For example, some animal influenza strains, such as the bird flu H5N1 virus (which fortunately never mutated to spread from person-to-person), have been associated with unusually aggressive disease, often with pneumonia and multi-organ failure and high death rates. In contrast, swine flu H1N1 associated with the 2009 epidemic was considered mild and no more dangerous than the seasonal flu, which is fortunate since it transmits easily from human to human.
Treatment: Two antiviral drugs, oseltamivir (Tamiflu) and zanamivir (Relenza), are approved for treatment of influenza. These drugs have reduced the severity and duration of human influenza and may be considered for treatment of swine flu. However, antiviral resistance has occurred among some cases of influenza and is being carefully monitored by health authorities. Always see your health care provider to determine whether or not you should take these medications, it depends on the duration of your symptoms and any underlying illnesses that may predispose you to complications.
Prevention: If you are in a high-exposure situation, your doctor may recommend medication to prevent getting swine flu. In general, other prevention tips to avoid contracting the flu include frequent hand washing and avoiding those who are sick. If you are sick with the flu or flu-like symptoms, cough or sneeze into a tissue or crook of your arm, wash your hands frequently, and stay home for at least seven days or 24 hours after your symptoms resolve (whichever is longer), and talk to your health care provider.
Sources:
Centers for Disease Control and Prevention. H1N1 Flu (Swine Flu). http://www.cdc.gov/h1n1flu/. Accessed April 24 – May 6, 2009.
World Health Organization. Epidemic and Pandemic Alert and Response. Influenza A (H1N1). http://www.who.int/csr/disease/swineflu/en/index.html. Accessed April 24 – May 6, 2009.
