The Facts

Swine influenza, also called "swine flu," is a contagious respiratory disease that affects pigs. Just like humans, pigs can get the flu. The swine flu can be passed from pig to pig by direct contact, indirect contact (e.g., a pig coming in contact with a surface that has the virus), or through tiny particles in the air.

Strains of swine flu virus usually only infect pigs, but they do sometimes infect humans, resulting in human swine flu. Since the pandemic of swine flu in 2009, the annual influenza vaccine has not been formulated to protect people from contracting this virus. Currently, there is no swine flu pandemic, although a number of cases have been reported both in Canada, as well as globally.


Swine flu is caused by a virus. The most common subtype, or strain, is influenza type A H1N1, and this subtype has also caused infection in people; however, this H1N1 swine flu virus is different from the H1N1 human virus. The letters H and N in the subtype name stand for proteins found on the surface of the virus, which are used to distinguish between different subtypes. Other virus subtypes found among pigs include H1N2, H3N1, and H3N2.

Influenza viruses are constantly changing their genes, a process called mutation. When a swine flu virus is found in humans, it is said to have "jumped the species barrier." This means that the virus has mutated in a way that allows it to cause the condition in humans. Because humans have no natural protection or immunity to the virus, they are likely to become ill.

Pigs can be infected by swine influenza, human influenza viruses, and avian (bird) influenza viruses. When a pig is infected with influenza viruses from different species, the viruses can swap genes and a new virus that is made up of genes from the various viruses from different species can appear.

Humans do not normally become infected with swine flu. However, there have been periodic human infections; most of these cases occur in people with direct exposure to pigs (e.g., people working on pig farms or slaughterhouses). Humans can become infected when pigs cough or sneeze, releasing infectious droplets into the air. People have also infected pigs with strains of human flu virus as well.

Person-to-person transmission of swine flu has been documented, but it is not clear how easily the virus is spread among people. It is believed that the virus spreads the same way as regular seasonal influenza. It may be spread from person to person when the virus enters the body through the eyes, nose, and/or mouth when coughing and sneezing. The virus can also rest on hard surfaces like doorknobs, ATM buttons, and counters. A person who touches these surfaces with their hands and then touches their eyes, mouth, or nose can become infected with the virus.

You cannot get infected with swine flu from eating pork products that have been properly cooked to an internal temperature of 71°C (160°F). The swine flu is not transmitted through food.

Symptoms and Complications

The symptoms of swine flu in humans are very similar to those of seasonal human influenza. People with swine influenza may experience:

  • cough
  • fever
  • loss of appetite
  • tiredness, lack of energy

Other reported symptoms of swine flu include runny nose, sore throat, nausea, vomiting, and diarrhea.

Some people have a higher risk of becoming seriously ill if infected. Children under 5 years old and people with weakened immune systems due to medications or health conditions such as AIDS are a few examples.

Making the Diagnosis

If you have recently travelled to an area of the world where there is a swine flu outbreak in humans, if you have been exposed to infected pigs (e.g. country fair, petting zoo, pig farm), and if you may be at high risk for a more severe infection (e.g., if you are pregnant or elderly or if you have asthma), you should see your doctor. Before you go to your doctor's office, call them ahead of time so that they can prepare for your visit, so that you do not infect them or others in the doctor's office waiting room.

A doctor can perform laboratory tests that can help identify the flu virus in addition to assessing your symptoms. Your doctor may take samples from your nose or throat to confirm swine flu infection.

Treatment and Prevention

There are vaccines for pigs to prevent swine flu; however, there is no vaccine currently available to protect humans from swine flu.

For people, there are medications available that may help in the prevention and treatment of swine flu. Certain types of antiviral medications (neuraminidase inhibitors), including oseltamivir and zanamivir, may be used to treat swine flu.

Over-the-counter medications such as acetaminophen (Tylenol®) can also help by relieving fevers and aches. It is also important to stay hydrated and get enough rest.

Most people with previously reported human swine flu have been able to recover fully without medical attention and without antiviral medications.

For people who are sick, help yourself get better and prevent the spread of the virus by doing the following:

  • Stay at home for at least 24 hours after your fever is gone. Do not go to work or school.
  • Stay at least 1 metre away from other people.
  • Rest and drink plenty of fluids.
  • Cover your mouth and nose with a tissue when coughing or sneezing. Throw your used tissue in the garbage. If you do not have tissue available, cough or sneeze into your sleeve or hands, away from others. Wash your hands thoroughly afterwards.
  • Wash your hands with soap and water throughout the day. Make sure to wash your hands with soap for at least 15 seconds. Use an alcohol-based hand sanitizer if you don't have access to soap and water.

There are ways to protect yourself from catching the swine flu virus. People who may be exposed to infected pigs or are travelling in areas where a swine flu virus outbreak has occurred need to take special precautions to reduce the chance of exposure to the swine flu virus. Here are some tips to prevent flu:

  • Avoid close contact with people who are sick and who have symptoms of swine flu (e.g., fever, cough).
  • Wash your hands with soap and water frequently and thoroughly. To ensure proper sanitization, you should wash your hands with soap for at least 15 seconds. Use alcohol-based sanitizers if hand-washing is not convenient.
  • Get an annual influenza immunization (flu shot).
  • Practice good health habits such as getting enough sleep, eating a nutritious diet, and staying physically active.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.

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