General information about influenza A (H1N1)

What is influenza A (H1N1)?

Influenza A (H1N1) is a virus that first occurred in pigs and has now developed into a disease in humans. Influenza originating from pigs occur in wild birds, domestic animals and human beings, but transmission between animal species is rare.

Is there reason for concern?

The overwhelming majority of people will experience only mild symptoms from influenza A (H1N1), which will be over in a few days. Therefore, the Danish National Board of Health does not consider that people living in Denmark need to be concerned.

The Danish National Board of Health and Statens Serum Institut monitor the situation closely and is in close contact with the WHO and the health authorities throughout Europe

Are children more susceptible to influenza A (H1N1)?

Children may contract influenza A (H1N1) like anyone else, but they are not more at risk. If a child has high fever for more than three days, you should call a doctor.

What is the difference between seasonal flu and influenza A (H1N1)?

Influenza A (H1N1) is a novel virus that the elderly are completely, or partially, immune to. Winter influenza, on the other hand, is caused by a virus that only changes slightly every year.

Consequently, many more people are immune to it.

Why is the new virus called influenza A (H1N1)?

The WHO has decided to name the new influenza type influenza A(H1N1). This name is more correct than the term 'swine flu', which is misleading because it causes people to believe that the disease is primarily found in pigs, just as a bird flu is found in birds.

How widespread is influenza A (H1N1)?

In Denmark, Statens Serum Institut (the Danish State Serum Institute) keeps watch over the spread of influenza A (H1N1). Statistics from the State Serum Institute are available in Danish here.

How long will the influenza pandemic last?

This is difficult to predict exactly, but Statens Serum Institute estimates that the epidemic will last between six and eight weeks, reaching its peak the end of November. It is to early to say if subsequent waves will occur and how long they will last.

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What if I get ill?

What are the symptoms of influenza A (H1N1)?

The symptoms are the same as with seasonal flu, i.e. sudden fever, sore throat, cough and muscle pain. Diarrhoea may also occur.

When should I call a doctor?

Call your doctor if you have influenza and experience difficulty breathing, shortness of breath or if fever continues for more than three days. Influenza may in serious cases cause pneumonia, which must be treated by a doctor. You should also call a doctor if a child younger than three years' of age has a high fever or stops drinking or refuses the breast. If you are pregnant and develop influenza symptoms, you should also contact your doctor.

What should I do if I get symptoms?

If you are otherwise in good health, you should act no differently than you would if you get the flu - which usually means staying at home. Call your doctor if your symptoms get worse.

Is there a treatment for Influenza A (H1N1)?

Influenza A (H1N1) can be treated with antiviral medicine such as Tamiflu®. There have been cases where the novel virus has shown resistance to Tamiflu®, but in the vast majority of cases Tamiflu is effective. Complications and consequences of influenza A (H1N1) are treated with antibiotics. In general, the disease can be treated as any other influenza with pain and fever-reducing medicine.

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Pregnancy and influenza A (H1N1)

Are pregnant women at an increased risk of serious influenza?

The overwhelming majority of women who come down with influenza during pregnancy go through it without problems. Pregnant women are not more likely to get novel Influenza A (H1N1) than anyone else, but if they do get it, they have a slightly higher risk of complications such as pneumonia and breathing difficulties.

Pregnant women should generally avoid any viral infection throughout pregnancy and not just influenza virus.

Pregnant women should practice good hygiene, which means that they should wash their hands carefully and avoid spending time with ill persons. Pregnant women who have influenza symptoms should call their doctor.

May pregnant women be vaccinated?

The Danish Health and Medicines Authority assesses that the vaccine can be given to pregnant women if it is considered necessary. There is nothing to indicate that vaccination of pregnant women increases the risk of deformities.

Read more about vaccination and pregnancy at the website of the National Board of Health.

Vaccination is recommended for pregnant women who are in a risk group. In the 1st trimester of pregnancy, vaccination is given upon individual assessment by a doctor. In the 2nd and 3rd trimesters of pregnancy, women can be offered vaccination upon their own wish.

How many vaccine doses are needed if you are pregnant?

The Danish National Board of Health recommends one vaccine dose for pregnant women. But if you are pregnant and have a weakened immune system, you should receive two vaccine doses.

Does the foetus obtain protection if a pregnant woman is vaccinated?

It is not known with certainty if the foetus is protected by the vaccine, but it is possible that the foetus may achieve some degree of protection.

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Vaccination and vaccine

Is the pandemic vaccine effective against influenza A (H1N1)?

The vaccine provides a very high degree of protection against the novel influenza. The degree of protection is highest among persons with an intact immune response and less effective in persons with a weakened immune response. The vaccine is expected to prevent a total of 70-90% of all disease cases among young, healthy persons. In the elderly, the degree of protection will be more limited.

If the influenza virus A (H1N1) changes much during the epidemic, the protection may diminish or cease to exist.

Who is to be vaccinated against influenza A (H1N1)?

Some people have an increased risk of becoming seriously ill if they are infected with influenza A(H1N1). This is why the Danish National Board of Health recommends that certain risk groups be vaccinated. In addition, the Danish National Board of Health and the Danish Ministry of Health and Prevention recommend vaccination for healthcare and nursing staff and persons in important functions in society.

Why is vaccination not recommended for everyone?

On the basis of current knowledge on novel influenza A(H1N1)v, the Danish National Board of Health estimates that the overwhelming majority of those who become infected will experience a mild disease course. Vaccination against influenza is primarily given with a view to preventing severe influenza illness or its complications.

Risk group persons are at increased risk of experiencing a more severe disease course when infected with influenza A (H1N1). Consequently, vaccination is recommended for the risk group persons defined by the Danish National Board of Health and in EPI-NYT 41/09 (weekly newsletter from the Statens Serum Institut) and for any nursing staff who may come into contact with such persons.

Are there any allergic persons who should not be vaccinated?

Persons with type 1 allergy to the ingredients, e.g. egg and chicken protein, formaldehyde and gentamicin, should not be vaccinated. You cannot be vaccinated if you are ill with fever.

Should immunosuppressed individuals receive vaccination?

Patients with congenital as well as acquired immunodeficiencies including splenectomised, HIV-infected and pharmacologically immunosuppressed patients should receive vaccination due to the increased risk of serious disease associated with influenza infection. If possible, vaccination should take place three weeks prior to initiation of immunosuppressive therapy.

May persons receiving anticoagulant therapy be vaccinated?

Persons in stable and well-controlled anticoagulant therapy may be vaccinated.

Should persons who have had influenza this year be vaccinated?

Persons who for whom influenza A has been confirmed by a doctor will not benefit from the vaccine (but may be vaccinated against seasonal influenza).

Persons who have had influenza-like disease which was not confirmed as influenza A (H1N1) should be vaccinated provided they belong to a risk group.

Does the vaccine contain live virus?

No. Consequently, it cannot cause influenza illness.

Why does the vaccine contain mercury?

The vaccine has been added the preservative thiomersal, which contains a small quantity of mercury. The quantity of mercury contained in the vaccine is considerably smaller than the amount of mercury you normally ingest with your food in a week.

There is no documentation that thiomersal, applied in the doses contained in the vaccine, pose a health risk. The substance is approved for use as a preservative in vaccines by pharmaceutical authorities worldwide and by the WHO.

How was it possible to approve the vaccine so fast?

Under normal circumstances it would take much longer to license a new medicine. In regard to pandemic vaccines, an agreement has been made between the European authorities and the vaccine manufacturers, allowing the manufacturers to submit data on a current basis and committing the authorities to assess such data on a current basis.

This has made it possible to shorten the approval process.

Does the vaccine have side effects?

Like other vaccines the pandemic vaccine can be associated with side effects. The most common side effects are soreness, redness and swelling at the vaccination site, muscle and joint pains, headache and fever within 1-2 days after the vaccination. The side effects generally recede within 1-3 days.

These side effects are expected and harmless. These side effects are seen a little more often than for the seasonal influenza vaccine.

Serious side effects are rare. The Danish Health and Medicines Authority monitors and evaluates potential, serious side effects. If injury is caused by vaccination, the Danish Patient Insurance may pay damages in accordance with standard provisions.

How does the Danish Health and Medicines Authority keep watch over side effects?

All reported side effects after vaccination are registered in the European pharmacovigilance database. The Danish Health and Medicines Authority continuously assess whether the reported side effects correspond to what may be expected, or whether unexpected serious adverse reactions have shown among the reported side effects.

How many injections are necessary?

The Danish National Board of Health recommends patients who belong to a risk group to be given one vaccine dose, unless they have a weakened immune system. The Danish National Board of Health furthermore assesses that pregnancy does not in itself reduce the effect of vaccination, and one vaccine dose is therefore recommended for pregnant women.

However, the National Board of Health recommends two vaccine doses to the following groups:

• Children under the age of 10 in an at-risk group.
• Patients with a weakened immune system (whether congenital, acquired or caused by other therapy). If there is doubt about whether the patient has a weakened immune system, and the patient has a history of repeated lung infections or other, two doses are given.

How long should the interval be between the two vaccine doses?

An interval of at least three weeks is required between the two injections.

May the influenza vaccine be given in conjunction with other vaccines?

The vaccine can be given in conjunction with the seasonal influenza vaccine and other vaccines.

May women who breastfeed be vaccinated?

Yes.

Will the seasonal influenza vaccine be effective against influenza A (H1N1)?

No, it is unlikely that the vaccine against the 'ordinary' seasonal influenza will have an effect on the novel influenza A (H1N1).

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How do I avoid infection?

How does influenza A (H1N1) spread?

Influenza A (H1N1) is passed on like any other ordinary flu. Influenza virus usually spreads from the onset of the first symptoms, e.g. sneezing, coughing, fever, etc., but the risk of spread is higher in the first days of illness. The incubation period - the time between infection to the first symptoms - is up to seven days. But most people will become ill within the first days.

The virus is considered not to spread if you have been fever-free for 24 hours and you otherwise feel well.

How do I avoid flu spread?

Influenza A (H1N1) is transmitted via small droplets from coughing and sneezing, etc. The virus may also be transmitted from surfaces such as door handles. If you want to avoid being infected and infecting others you should therefore:

• Avoid close contact with people you know are ill.
• Stay home from work, school, etc. if you are ill.
• Avoid coughing or sneezing in your hands, use your sleeve or a disposable handkerchief instead.
• Wash your hands frequently with soap - especially if you cough and sneeze. By doing so, you reduce the risk of infecting others and getting ill yourself.
• Avoid touching your eyes, nose or mouth. By doing so, you reduce the risk of infection even if you have traces of the virus on your hands.

Is it safe to travel abroad?

The Danish National Board of Health does not advise against travelling abroad - not even against trips to the USA, Mexico or other countries where the risk of spread is high. We generally recommend travellers to keep up to date on the current situation in the country of destination and to follow the advice of local authorities and the WHO.

For further travel information, please visit the website of the Ministry of Foreign Affairs of Denmark (information is only available in Danish).

Does it help to wear a mask?

There is no need for the general Danish public to wear a mask, but the Danish National Board of Health does recommend doctors and other healthcare staff to wear a medical mask and other protective equipment if they are in direct contact with patients who are being examined for possible infection with influenza A (H1N1).

The Danish National Board of Health does not recommend other people to wear a mask, meaning that other staff in the healthcare sector or general public do not need to wear a mask or other protective equipment.

Should I stop eating pork?

No, you cannot get the novel influenza from eating pork – or being near pigs.