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Overview

 

Definition

Swine influenza or swine flu is a respiratory disease of pigs caused by type A influenza virus that regularly infects pigs. Swine flu viruses do not normally infect humans; however, human infections with swine flu do occur and cases of person-to-person spread of these viruses have been documented.

Swine flu viruses cause high levels of illness and low death rates in pigs. These viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.

Swine Flu in Humans

Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in persons with direct exposure to pigs – for example, children near pigs at a fair or workers in the swine industry. In addition, cases have been documented of one person spreading swine flu to others.

How many swine flu viruses are there?

Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can re-assort, swapping genes, and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 or H3N2 viruses.

How common is swine flu among pigs?

H1N1 and H3N2 swine flu viruses are endemic among pig populations in North America and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months in the late fall and winter and sometimes with the introduction of new pigs into susceptible herds. Studies have shown that the swine flu H1N1 is common throughout pig populations worldwide, with 25 percent of animals showing antibody evidence of infection. Human infections with swine flu H1N1 viruses are rare.  

Symptoms

The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include high fever, cough, headache, general aches, fatigue, eye pain, shortness of breath, and lack of appetite. Some people with swine flu have also reported runny nose, sore throat, nausea, vomiting and diarrhea.  

Causes

Influenza viruses can be directly transmitted from pigs to people and from person to person. Human infection with flu viruses from pigs are most likely to occur when people are in near infected pigs, such as in pig barns or livestock exhibits and pigs at fairs.

Spread of swine flu from person to person can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly spread person to person through coughing or sneezing by people infected with the influenza virus. People may become infected by touching something with flu viruses or germs on it and then touching their mouth or nose. Germs on hard surfaces, such as counters and doorknobs, can be picked up on hands and spread to the respiratory system when people touch their mouth or nose.

Who's most at risk?

  • Those with underlying medical illness such as asthma, lung disease, heart disease, diabetes, cancer or those with weakened immune systems;
  • Those with a cough and high fever (over 39.5°C) or shortness of breath;
  • Pregnant women.

Can people catch swine flu from eating pork?

No. Swine influenza viruses are not transmitted by food. You can not get swine flu from eating pork or pork products. Eating properly handled and cooked pork or eating pork products is safe. Cooking pork to an internal temperature of 160°F (70°C) kills the swine flu virus as it does other bacteria and viruses.  

 

Tests and Diagnosis

To diagnose swine influenza A infection, a respiratory specimen would need to be collected generally within the first four to five days of illness, during the time when an infected person is most likely to be shedding the virus. However, some persons, especially children, may shed the virus for 10 days or longer.

Identification of swine flu influenza A virus requires sending a specimen from the person with the infection to the BCCDC Public Health Microbiology & Reference Laboratory within PHSA Laboratories.  

Treatment and Drugs

Antiviral drugs can be used for early treatment of the illness. Antivirals may mainly be used while a vaccine for the strain in question is being developed and manufactured. Both Canada and B.C. have purchased an advance supply of antivirals and have committed to purchasing more, as part of emergency public health and preparedness planning.

Canada has a plan and contract with a manufacturer to research and produce a vaccine for an influenza pandemic virus once it is identified, so production can start as soon as possible.  

Prevention

 You can reduce the risk of getting swine flu or spreading it to others by taking standard precautionary measures:
  • Wash your hands regularly, especially after you cough or sneeze.
  • Cover your nose and mouth with a tissue when you cough or sneeze, and throw the tissue in the trash after you use it.
  • Avoid touching your eyes, nose or mouth, as germs can spread that way.
  • Avoid close contact with people who are sick.
  • If you get sick, stay at home and limit contact with others to keep from infecting them.

Is there a vaccine available?

Yes. Both adjuvanted and non-adjuvanted H1N1 vaccines are now available.

Who should get the vaccine now?


As of November 20, all BC residents who want to be immunized against the H1N1 flu virus are eligible to receive the free vaccine.

Not everyone will be able to be immunized immediately, since vaccine supply varies regionally.

Each area is gauging supply and demand, and there may be some differences in timing of vaccine availability.

Go to the online Flu Clinic Locator to find a clinic near you, or contact your family doctor.

Initially, those who would most benefit and those at highest risk were recommended to receive the vaccine first. This included:
  • Pregnant women
  • People under 65 with chronic medical conditions
These chronic conditions include:
  • Heart or lung disorders that require regular medical care including asthma, chronic obstructive pulmonary disease, or cystic fibrosis
  • Kidney disease, diabetes, cancer, anemia, or weakened immune systems
  • Those with health concerns causing difficulty breathing, swallowing, or a risk of choking on food or fluids, including persons with severe brain damage, spinal cord injury, seizures or neuromuscular disorders
  • Children and teenagers taking Aspirin (ASA) for long periods of time
People residing in remote and isolated communities were also targeted starting October 26.

Beginning the week of November 2, the following groups were targeted to get the vaccine:
  • Health care workers in critical areas such as ER, ICU, and specialized units
  • Children between 6 months and less than 5 years of age
  • Household contacts younger than 65 years of age of: babies less than six months old and of severely immunocompromised people
Beginning the week of November 9, the immunization program expanded to include:
Other health care workers, with priority given to those in critical functions and direct patient care roles
Women in the first half of pregnancy (using unadjuvanted vaccine)

For the week of November 16th, the following additional groups were recommended for receipt of the vaccine:
  • Health care workers in acute care, long-term care, home care, and public health
  • Children from 6 months to 18 years of age
  • First Responders

Is the H1N1 swine flu virus the same as human H1N1 viruses?

No. The H1N1 pandemic is very different from typical influenza seasons. While H1N1 infections, so far, have been generally mild, H1N1 is infecting more and younger people than usual. It is very unusual to have a higher risk of severe influenza infection among younger people. Compared with seasonal influenza, we are expecting a greater proportion of the young population to suffer severe outcomes. 
 

For more information on the H1N1 vaccine, visit ImmunizeBC

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Last Updated: November 19, 2009