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Swine Flu
(Novel H1N1 Influenza)

Note: This article was updated on 10/26/2009. The situation with novel H1N1 ("swine flu") is fluid and likely to change. The reader is referred to the U.S. Centers for Disease Control and Prevention (CDC) web site (www.cdc.gov) for current information.

Swine Flu Symptoms...What to Do? One ER Doctor's Perspective

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editors: Melissa Conrad Stöppler, MD

What does a person do if they suspect they have swine flu?

As cases of swine flu are being confirmed around the world, governments are ramping up their disease control plans to hopefully minimize the effects of this infection. According to the World Health Organization, "Given the widespread presence of the virus...containment of the outbreak is not feasible. The current focus should be on mitigation measures." This means that preventing spread of the virus is not likely, and treating outbreaks will be important in minimizing the numbers of people who might become ill and potentially die.

Swine flu is no different that any other influenza-like disease when it comes to symptoms:

fever,
cough,
sore throat,
chills,
body aches, and
fatigue.

Aside from the chills and shakes, these sound similar to the symptoms of a severe cold. Whether that's all there is or whether a person will become significantly ill is difficult to predict. Individuals with poor immune systems, such as infants and the elderly, those undergoing chemotherapy treatment, or taking medications that impair immunity, are at higher risk for more severe illness. But even healthy people can become sick. The virus spreads by aerosol droplets, meaning that secretions from an infected person can be spread into the air by coughing or sneezing. It's the close contact with an ill person that causes the disease to spread. And a person may be contagious for 24 hours before any symptoms occur.

How a community, a hospital, or an individual deals with the potential for infection will help decide how fast and how far it will spread.

Read about prevention of swine flu »

Top Searched Swine Flu Terms

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Complete swine flu pandemic coverage on WebMD

Swine Flu History and Overview

Influenza viruses are small RNA viruses that infect many mammals, including humans, birds, and swine. Before 2009, swine influenza predominately affected swine and was not transmitted often or easily to people. Even in the isolated instances in which swine influenza infected people, it had very limited ability to spread from person to person. Most cases were directly linked to contact with swine through farming or at fairs.

Swine were first noticed to have influenza-like illnesses in 1918 during the human influenza pandemic. The term "pandemic" means that an infection has spread to many countries around the world, causing widespread human disease. Swine influenza did not cause the 1918 pandemic. Rather, pigs apparently acquired the infection from humans or from an undiscovered source. For decades, the swine virus remained relatively unchanged. In the 1990s, however, swine influenza viruses became more diverse and new strains appeared. The reason for this change is not clear but may have been related to overcrowding on large swine farms.

Before 2009, there was only one swine influenza outbreak in people that caused public-health concerns. This outbreak occurred in 1979, in soldiers at Fort Dix, New Jersey. One recruit died, and approximately 12 were hospitalized with influenza. Further testing showed that more than 200 recruits had acquired the virus, although most had few or no symptoms. The infecting strain was found to be strongly related to swine influenza virus, raising concerns that a new pandemic might occur. In response, public-health officials began a massive public vaccination program. Up to 25% of people in the United States were vaccinated. Unfortunately, the 1979 vaccine was associated with a small increased risk of Guillain-Barré syndrome, a serious neurological condition, with the risk estimated to be one to nine excess cases per million doses. Importantly, the 1979 strain did not spread easily from person to person and there was no epidemic. Human cases outside of Fort Dix were uncommon. Moreover, the 1979 vaccine was made using an old-fashioned process which is no longer utilized.

The lessons learned from the 1979 swine influenza event have been applied in dealing with pandemic threats, including the severe acute respiratory syndrome (SARS) outbreak of 2003 and the 2009 influenza outbreak. Key lessons include ensuring adequate communication with the public, producing a rapid but measured response to potential threats, and ensuring that any new strain fulfills criteria to cause a pandemic before large-scale vaccination is undertaken.

The 2009 outbreak of swine influenza (novel H1N1)

In March and April 2009, hundreds of cases of human respiratory illness were reported in Mexico that were suspected or confirmed to be caused by a novel swine-type influenza virus. By April, confirmed cases were also reported in the United States. The first reported cases in the U.S. came from San Diego County and Imperial County in California and Guadalupe County in Texas. Reports from other states rapidly followed, and the disease spread rapidly around the globe. The World Health Organization (WHO) has officially declared the 2009 swine flu to be a pandemic. The U.S. Centers for Disease Control and Prevention (CDC) estimates that more than 1 million Americans were infected with swine influenza by June 2009. By August 2009, more than 170 countries and territories reported swine flu cases. By October, 46 U.S. states were reporting widespread outbreaks. By late October, the virus had been confirmed to have caused more than 1,000 deaths in the U.S., with almost 100 of the deaths in children. Approximately 6% of deaths are in pregnant women, although only 1% of the population is pregnant. Physician visits, hospitalizations, and deaths in the fall of 2009 all exceeded seasonal thresholds. On Oct. 25, 2009, President Obama declared a national emergency as a result of the outbreak. This allows public-health officials additional power to allow waive some regulations to facilitate patient care and will allow hospitals to set up separate facilities to isolate sick patients.