What is influenza? How did it originate?
Seasonal influenza, known as the ‘flu’, is a common acute respiratory infection caused by influenza viruses. First arising around 6,000 years ago, these viruses are thought to have spread to humans through the domestication of animals.
Symptoms of influenza
Flu symptoms include fever (a temperature of 38 degrees celsius or above), headaches and muscle aches, fatigue, a sore throat, cough, insomnia, loss of appetite, nausea, vomiting, stomach pain and diarrhoea. With flu, these symptoms often manifest very quickly and patients may even be able to remember the hour that they began feeling sick.
Children may also suffer from ear pain and be less active.
Transmission and Seasonality
The flu is caused by germs that are spread through coughs and sneezes. These germs can live on surfaces including hands for up to 24 hours.
In temperate places, flu epidemics are seasonal, occurring during the winter. In tropical countries such as Singapore, outbreaks can occur throughout the year.
What are the risk areas in the world?
Influenza causes illness in all parts of the world, from mild symptoms to severe illness and even death.
Most people who die from flu-related illness in industrialized countries are over 65, while research suggests that 99 percent of children under 5 who die from flu-related illnesses are in developing countries.
What is an influenza certificate?
An influenza certificate proves that you have had the flu vaccination. It is not normally a requirement for travel.
Is influenza curable?
There’s no cure for the influenza virus but the symptoms can be managed and most people will recover in around a week.
However some groups are more at risk of becoming seriously ill due to the flu virus. They include people over 65, women who are pregnant, those who have a long term health condition and those with a weak immune system.
Influenza prevention
The Ministry of Health (MOH) Singapore recommends getting vaccinated with the flu vaccine ideally before peak flu season starts (in Singapore, from December to February and again from May to July). The vaccine reduces the risk of catching the flu, as well as spreading it to others.
The influenza vaccination is part of the National Adult Immunisation Schedule initiated by the Ministry of Health. The schedule stipulates that adults get one shot of the flu vaccine every year as the strains may vary year to year.
You can also help prevent the spread of flu by:
- washing your hands with soap and warm water often
- drying your hands properly after washing them
- catching your cough or sneeze in a tissue, and throwing it away as quickly as possible.
You should:
- avoid touching your face, eyes or mouth with your hands
- stay away from others if you feel feverish or have other symptoms
- avoid close contact with sick people.
How long before a trip do you have to get the influenza vaccine?
You should get vaccinated at least two weeks before travel to give your body enough time to fully develop the antibodies that protect you from catching the flu.
Who should get the influenza vaccine?
Usually flu will clear up on its own after around a week. However, it can cause more serious complications including pneumonia for some groups of people.
MOH’s National Adult Immunisation Schedule recommends that the following groups of people get 1 dose of the flu vaccine annually:
- Persons aged 65 years or older;
- Persons aged 18 years and receiving long-term aspirin therapy;
- Persons who have chronic medical conditions such as diabetes mellitus, asthma, and heart disease;
- Persons who are immunocompromised;
- Persons receiving intermediate and long term care services;
- Women at all stages of pregnancy.
Who should not get the influenza vaccine?
Most people can have the flu vaccine. However, if you’ve had a serious allergic reaction to the flu vaccine previously, you should avoid it.
The influenza vaccine is usually made by growing the vaccine in chicken eggs so small amounts of the protein may remain in the vaccine. If you have an egg allergy, you can get a version that is egg-free or has a low egg content. You should be extra cautious if your egg allergy is severe and you have previously been admitted in intensive care for a severe anaphylactic reaction to egg. You doctor will be able to advise you further.
If you have a fever you should postpone your vaccination until you have recovered.
What is the minimum age requirement for the influenza vaccine?
Children over 6 months can get the flu vaccine. The Health Promotion Board recommends that children aged between 6 months and 5 years old get vaccinated every year as flu viruses are constantly evolving.
Your doctor or travel health professional can advise you further.
What is the effectiveness of the influenza vaccine?
The flu vaccine is the best method of protection we have against influenza. It is not guaranteed 100 percent effective, but even in the rare case you do get the flu after vaccination, you’ll likely experience milder symptoms and recover quicker than if you hadn’t been vaccinated.
Protection reduces over time and new strains of flu develop, so yearly vaccinations are recommended.
What are the side effects of the influenza vaccine?
Side effects of the flu vaccine include mild fever, and muscle aches which last around a day or two.
The injection may cause a sore arm for a few days.
Some people think the vaccine’s side effects are symptoms of catching the flu, but the virus you are given is inactive. This makes it impossible to catch the flu from the flu vaccine.
Dosage and Duration
Different flu vaccines (trivalent and quadrivalent) are recommended for different age groups. Adults usually require one injection to develop immunity.
Children between the ages of 6 months and 8 years who have not received the flu vaccine previously or who have only received one dose of the flu vaccine previously may require two doses of the vaccine to be fully protected. Your travel health professional or GP will be able to evaluate this on a case-by-case basis and give you the appropriate recommendation.
The protection provided by the flu vaccine reduces over time, so the Ministry of Health recommends getting vaccinated every year.
When and where was the last outbreak of influenza?
Influenza outbreaks cause between 3 and 5 million severe cases of illness and between 290,000 and 650,000 deaths each year.
The last major pandemic was swine flu in 2009, caused by the flu virus known as H1N1. It was named for its similarity to a flu that affects pigs and affected mainly young people, who had less immunity to it. H1N1 is now included in the annual flu vaccine.
