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Health Library - Influenza (flu, including Swine flu)
What is swine flu?
Swine flu is a type of flu (influenza). It usually affects pigs but it can also affect humans. The virus can be transmitted from human-to-human. Before spring 2009, the virus rarely passed from human-to-human.
A new strain of the swine influenza virus called influenza H1N1v that spreads easily from human-to-human emerged in Mexico in spring 2009. It has now spread to affect people in other countries, including the UK. When a strain of influenza spreads easily between humans and causes many cases in several countries, this is called a pandemic.
What are the symptoms of swine flu?
The symptoms are similar to the symptoms of 'ordinary' flu. Typically, if you have swine flu:
- You will usually have a high temperature (fever) of 38ŶC or greater.
- You would normally also have at least two of the following symptoms: cough, sore throat, headache, runny nose, and general aches and pains affecting the muscles and joints.
- You may also have any of the following: fatigue (tiredness), loss of appetite, diarrhoea, nausea (feeling sick), vomiting, abdominal pain, ear pain from an ear infection, and, rarely, seizures.
In most cases, the symptoms usually last for a few days. Typically, symptoms then gradually ease off and are usually gone within 7-10 days. An irritating cough may persist for a week or so after other symptoms have gone.
The incubation period (that is, the time between contracting the virus and the development of symptoms) is thought to be between two and five days, but may be up to seven days.
How is swine flu diagnosed?
The diagnosis is usually made by the typical symptoms. Because so many people now possibly have swine flu, a swab test to confirm the diagnosis is now impractical. Therefore, a 'probable' diagnosis is made by the typical symptoms.
What are the possible complications of swine flu?
Most people fully recover. However, complications occur in some people and they can be serious and life-threatening. The most common serious complication is pneumonia (lung infection). This can be severe and is fatal in some cases. If death occurs as a result of swine flu it is usually due to a severe pneumonia. The pneumonia may be due to the virus itself but can also be due to a 'secondary' infection by a bacterium (a different type of germ). Other rare complications include encephalitis (inflammation of the brain) and myocarditis (inflammation of the heart muscle).
People most at risk of developing complications are those who already have other medical problems. In particular, those with ongoing chest diseases such as asthma or chronic obstructive pulmonary disease (COPD).
Consult a doctor urgently if you are concerned that a complication is developing. For example, if symptoms become severe or if other serious symptoms develop such as:
- Fast breathing, difficulty breathing or shortness of breath
- Chest pains
- Coughing up blood
- Drowsiness or confusion
What is the treatment of swine flu?
Unless you become very ill you will be treated at home. This will reduce the risk of the virus spreading to other people. Treatment consists of general measures, antiviral medication, antibiotics in some situations, and admission to hospital for the small number of people who become very ill (usually because of a complication that develops).
As with other flu-like illnesses, paracetamol and/or ibuprofen can lower your temperature, and also ease aches and pains. Drink plenty of fluids to prevent dehydration. It is best not to smoke. Decongestant drops, throat lozenges and saline nose drops may be helpful to ease nose and throat symptoms. But note: parents and carers should not use over-the-counter cough and cold medicines in children under six years old. There is no evidence that they work and they can cause side-effects such as allergic reactions, effects on sleep or hallucinations.
If it is suspected that you have swine flu then you will normally be offered treatment with antiviral medication. The antiviral drug most commonly used is called oseltamivir (trade name Tamiflu®). Another drug called zanamivir (trade name Relenza®) is sometimes used, especially in pregnant women and people with certain kidney diseases who have swine flu.
In particular, people considered at higher risk of developing complications are recommended to take antiviral medication as soon as possible after symptoms develop. People at higher risk include:
- Children under five years old
- Adults aged 65 years and older
- Pregnant women
- People of any age with:
o A poor immune system (for example, if you have HIV/AIDS, if you are receiving chemotherapy or steroid treatment).
o Chronic (ongoing) lung disease or asthma which has been medically treated within the last three years.
o Heart disease.
o Diabetes or another metabolic disorder.
o Chronic (ongoing) liver disease.
o Cystic fibrosis.
o Neurological conditions such as cerebral palsy, stroke, multiple sclerosis or muscular dystrophy.
o Sickle cell disease.
o Renal (kidney) disease.
Antiviral medication does not kill the virus but interferes with the way the virus multiplies. Therefore, antiviral medication does not cure swine flu, or offer long-term protection against swine flu. If you were not to have antiviral medication you are still likely to make a full recovery. However, antiviral medication reduces the risk of developing complications and may reduce the severity and duration of symptoms. Usually, treatment is taken for five days.
Antiviral medication is generally considered safe. However, as with any drug, there is a small risk from side-effects or reactions. For example, a small number of people who take Tamiflu® develop nausea, vomiting, diarrhoea, abdominal pain, and headache. These are usually temporary and usually soon go away. Serious side-effects such as dangerous allergic reactions (anaphylaxis) have been reported, but are rare. If you are prescribed an antiviral drug, read the information that comes with the drug for a full list of possible side-effects and cautions.
Pregnant women with swine flu are usually given Relenza®, which is an alternative to Tamiflu®. As this drug is inhaled it means that less of the drug is absorbed into the blood stream so is safer to take in pregnancy. Treatment with antiviral medication when you are pregnant will help to reduce symptoms such as fever and this may benefit the developing baby. If you are breast-feeding then you can still take an antiviral drug.
Treatment with antiviral medication should start as soon as possible, ideally within 12-48 hours of the onset of symptoms. However, you may get some benefit from treatment even if it is started up to seven days after symptoms began. In England, if you are prescribed an antiviral drug you will be given a unique access number and told where the nearest antiviral collection point is. You should then ask a friend or relative who doesn't have swine flu to go and pick up the antiviral drug. The friend or relative must show their own ID as well as that of the patient.
Antibiotics do not kill viruses such as the swine flu virus. Antibiotics are not routinely used for people with 'straightforward' swine flu who are normally healthy.
However, a complication that develops in some people with swine flu is a pneumonia that is a 'secondary' infection due to a bacterium. Other 'secondary' bacterial infections that sometimes occur include a bacterial tonsillitis and an ear infection. Therefore, a course of antibiotics is likely to be advised if you develop a complication such as pneumonia, tonsillitis, or ear infection.
Also, a course of antibiotics is likely to be advised as a 'precaution' to people with swine flu who are at increased risk of developing complications (listed above). The aim is to prevent possible secondary bacterial infections such as a bacterial pneumonia.
Admission to hospital
A small number of people with swine flu (less than 1 in 100 cases) become ill enough to need hospital admission. About 1 in 6 people admitted to hospital with swine flu needs high dependency care or intensive care treatment. Some of these people die. Compared with the number of people who actually get swine flu, the number of people who die from this disease is very small.
Should those who have been in contact with people with swine flu be treated as a precaution?
Giving treatment to all contacts is not currently recommended. The current recommendation is that if you are in a high-risk group (detailed above) and have been in prolonged contact with a person with swine flu, then treatment with antiviral medication may be considered.
Examples of 'prolonged contact' include that you are living and/or sleeping in the same household, you are a pupil in the same dormitory, or you are a boy/girlfriend of a person with swine flu.
How can swine flu be prevented?
People with symptoms of flu should stay at home until they feel better. General hygiene is important to reduce the spread of swine flu (and other diseases). This includes:
- Covering your nose and mouth when coughing or sneezing, using a tissue when possible.
- Disposing of tissues promptly.
- Washing your hands frequently with soap and water.
- Cleaning hard surfaces (such as door handles and work surfaces) frequently.
- Ensuring children also follow this advice.
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