Technically, the term "swine flu" refers to influenza in pigs. Occasionally, pigs transmit influenza viruses to people, mainly to hog farmers and veterinarians. Less often, someone infected with swine flu passes the infection to others.
In the spring of 2009, scientists recognized a particular strain of flu virus known as H1N1. This virus is actually a combination of viruses from pigs, birds and humans. During the 2009-10 flu season, H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu. Because so many people around the world got sick that year, the World Health Organization declared the flu caused by H1N1 to be a global pandemic.
In August 2010, the World Health Organization declared the pandemic over. Since that time, scientists have changed the way they name viruses. The H1N1 virus is now known as H1N1v. The v stands for variant and indicates that the virus normally circulates in animals but has been detected in humans. Since 2011, another strain, H3N2v, has been circulating in humans and also causes the flu. Both strains are included in the flu vaccine for 2018-19.
The signs and symptoms of swine flu are similar to those of infections caused by other flu strains and can include:
- Fever (but not always)
- Sore throat
- Runny or stuffy nose
- Watery, red eyes
- Body aches
- Nausea and vomiting
Flu symptoms develop about one to three days after you're exposed to the virus.
When to see a doctor
It's not necessary to see a doctor if you're generally healthy and develop flu signs and symptoms, such as fever, cough and body aches. Call your doctor, however, if you have flu symptoms and you're pregnant or you have a chronic disease, such as asthma, emphysema, diabetes or a heart condition, because you have a higher risk of complications from the flu.
Influenza viruses infect the cells that line your nose, throat and lungs. The virus enters your body when you inhale contaminated droplets or transfer live virus from a contaminated surface to your eyes, nose or mouth.
You can't catch swine flu from eating pork.
If you've lived in or traveled to an area where many people are affected by swine flu, you may have been exposed to the virus.
Swine farmers and veterinarians have the highest risk of exposure to true swine flu because they work with and are near pigs.
Influenza complications include:
- Worsening of chronic conditions, such as heart disease and asthma
- Neurological signs and symptoms, ranging from confusion to seizures
- Respiratory failure
The Centers for Disease Control and Prevention recommends annual flu vaccination for everyone age 6 months or older. Flu vaccines for 2018-19 protect against the viruses that cause swine flu and one or two other viruses that are expected to be the most common during flu season.
The vaccine is available as an injection or a nasal spray. The nasal spray is approved for use in healthy people 2 through 49 years of age who are not pregnant. The nasal spray isn't recommended for some groups, such as pregnant women, children between 2 and 4 years old with asthma or wheezing, and people who have compromised immune systems.
These measures also help prevent flu and limit its spread:
- Stay home if you're sick. If you have the flu, you can give it to others. Stay home for at least 24 hours after your fever is gone.
- Wash your hands thoroughly and frequently. Use soap and water, or if they're unavailable, use an alcohol-based hand sanitizer.
- Contain your coughs and sneezes. Cover your mouth and nose when you sneeze or cough. Wear a face mask if you have one. To avoid contaminating your hands, cough or sneeze into a tissue or the inner crook of your elbow.
- Avoid contact. Stay away from crowds if possible. And if you're at high risk of complications from the flu — for example, you're younger than 5 or you're 65 or older, you're pregnant, or you have a chronic medical condition such as asthma — consider avoiding swine barns at seasonal fairs and elsewhere.
To diagnose flu, including swine flu, your doctor will likely conduct a physical exam, look for signs and symptoms of influenza, and possibly order a test that detects influenza viruses.
There are several tests used to diagnose flu, but not everyone who has the flu needs to be tested. In most cases, knowing that someone has the flu doesn't change the treatment plan. Doctors are more likely to use a test to diagnose flu if:
- You're already in the hospital
- You're at high risk of complications from the flu
- You live with someone who is at greater risk of flu complications
Your doctor may also use a test to determine whether a flu virus is the cause of your symptoms, or if you have or are showing signs of another problem besides the flu, such as:
- Heart problems, such as heart failure or an infection of the heart muscle
- Lung and breathing problems, such as asthma or pneumonia
- Brain and nervous system problems, such as encephalopathy or encephalitis
- Septic shock or organ failure
The most commonly used test is called a rapid influenza diagnostic test, which looks for substances (antigens) on a swab sample from the nose or back of the throat. These tests can provide results in about 15 minutes. However, results vary greatly and are not always accurate. Your doctor may diagnose you with influenza based on symptoms, despite a negative test result.
More-sensitive flu tests are available in some specialized hospitals and labs.
Most people with flu, including swine flu, require only symptom relief. If you have a chronic respiratory disease, your doctor may prescribe additional medications to help relieve your symptoms.
There are four FDA-approved antiviral drugs that are sometimes prescribed within the first day or two of symptoms to reduce the severity of symptoms and possibly the risk of complications. These include:
- Oseltamivir (Tamiflu)
- Zanamivir (Relenza)
- Peramivir (Rapivab)
- Baloxavir (Xofluza)
But flu viruses can develop resistance to these drugs.
To make development of resistance less likely and maintain supplies of these drugs for those who need them most, doctors reserve antivirals for people at high risk of complications and those who are in close contact with people who have high risk of complications.
High-risk groups include people who:
- Are in a hospital, nursing home or other long-term care facility.
- Are younger than 5 years of age, particularly children younger than 2 years.
- Are 65 years old or older.
- Are pregnant or within two weeks of delivery, including women who have had pregnancy loss.
- Are younger than 19 years of age and are receiving long-term aspirin therapy. Using aspirin during a viral illness increases the risk of developing Reye's syndrome, a rare but potentially fatal disease, in these individuals.
- Are morbidly obese, defined as having a body mass index above 40.
- Have certain chronic medical conditions, including asthma, emphysema, heart disease, diabetes, neuromuscular disease, or kidney, liver or blood disease.
- Are immunosuppressed due to certain medications or HIV.
- Are American Indians or Alaska Natives Alaskans.
If you develop any type of flu, these measures may help ease your symptoms:
- Drink plenty of liquids. Choose water, juice and warm soups to prevent dehydration.
- Rest. Get more sleep to help your immune system fight infection.
- Consider pain relievers. Use an over-the-counter pain reliever, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others), cautiously. Also, use caution when giving aspirin to children or teenagers.
Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome.
Remember, pain relievers may make you more comfortable, but they won't make your symptoms go away faster and they have side effects. Ibuprofen may cause stomach pain, bleeding and ulcers. If taken for a long period or in higher than recommended doses, acetaminophen can be toxic to your liver.