Influenza ("flu") is an infection caused by a virus called the influenza virus. Symptoms of influenza, such as fever, cough, sore throat, runny nose, muscle ache, and tiredness are usually more severe compared to the common cold, which is caused by other respiratory viruses.

In temperate countries, influenza cases are seen mostly in colder and drier months during winters (usually the months of December to February for countries in the Northern Hemisphere and months of April to June for countries in the Southern Hemisphere).  In tropical countries like Singapore where there are no seasons, it has been observed that influenza cases peaked during the months of April to July and November to January (roughly similar to the months when peaks in influenza activities are observed in the Northern and Southern Hemispheres) though there are far fewer cases of influenza in Singapore than in the hemispheric countries. 

Circulating strains refer to the strains of influenza identified in the population.  Data from the Singapore National Influenza Viral Surveillance showed that proportion of circulating strains changes throughout the year with influenza A with (H3N2) as the predominant strain.  The other strains include influenza B and influenza A (H1N1). 

While most people with influenza recover with rest and symptomatic treatment, influenza can result in pneumonia requiring hospitalization or even death, especially in vulnerable groups such as very young children, the elderly and patients with chronic illnesses. There are about 1 to 2 deaths directly caused by influenza every year. A 2006 study indirectly estimated that influenza is associated with about 600 deaths (out of about 15,000) in Singapore every year, mainly in people over 65 years old. It is thought that influenza could weaken the health of vulnerable groups such as the elderly or people with chronic illnesses, so that they die from other causes.  In contrast, the World Health Organization (WHO) estimated that the annual epidemics of influenza in Northern and Southern Hemispheres' countries result in 3 to 5 million cases of severe illness and 250,000 to 500,000 deaths each year. 

Studies have shown that influenza virus can survive on environmental surfaces and can infect a person for up to 2-8 hours after being deposited on the surface.

2009 Influenza A (H1N1), also written as ‘Influenza A (H1N1-2009)’ (previously referred to as "new strain of swine flu") is a new strain of influenza virus that spreads from human to human.  As this is a new strain of virus, most people will not have resistance, and it can potentially spread quickly and infect a large proportion of the population in a short period of time.

Influenza A (H1N1-2009) spreads from human to human in the same way as seasonal flu. Flu can be spread when an infected person coughs, sneezes, or speaks. The flu viruses are transmitted into the air through droplets and other people breathe in the viruses. When these viruses enter the nose, throat, or lungs of a person, they begin to multiply, causing symptoms of the flu. The viruses can also be spread indirectly when a person touches a surface with flu viruses on it (for example, a door knob) and then touches his or her nose or mouth. Transmission can also occur when an infected person shares food with others during mealtime without a serving spoon.

The incubation period for the virus is estimated to range from 1 to 7 days.

At the current time, it is believed that this virus has the same properties in terms of spread as seasonal flu viruses. With seasonal flu, studies have shown that people may be contagious from one day before they develop symptoms to up to 7 days after they get sick.  Children, especially younger children, might potentially be contagious for longer periods.

To diagnose Influenza A (H1N1-2009), a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding the virus). However, some persons, especially those who are immuno-compromised may shed the virus for 10 days or longer.

Persons who have been infected with pandemic Influenza A (H1N1-2009) infection during the current first wave are likely to have some immunity against possible future waves of infection. Future changes in the virus would mean that the degree of immunity cannot always be predicted.

According to WHO, the majority of cases have occurred in people under the age of 25 years and around one third to half of the severe and fatal infections are occurring in previously healthy young and middle-aged people. 

While the overall risk of death for H1N1 is similar to normal seasonal flu,  the risk groups are slightly different. In normal flu, those over 65 years old are at highest risk along with the very young, under five years. But for H1N1, younger adults and those with underlying medical problems, such as chronic problems with breathing (e.g. asthma), diabetes, gross obesity, low immunity or who are pregnant appear to be at higher risk of complications from the infection.

Other H1N1 strains (not the 2009 strain) already infect humans every year, and their genes have originated from swine, human and avian sources. This is a characteristic of all human influenza viruses, so just having a hybrid virus with different origins is not a new finding.

However, when the hybrid virus appear to change significantly from current strains, the impact on transmissibility and virulence cannot always be predicted, and we need to link the genetic changes to what we observe in the community and in the affected individuals. For Influenza A (H1N1-2009), more epidemiological studies will be needed to better define how easily it spreads or whether it causes more severe disease.  Scientists are interested in the hybrid nature of H1N1 because it helps them to track its spread and origin more easily.

Historically, influenza pandemics have encircled the globe in two, sometimes three, waves. During the previous century, the 1918 pandemic (or "Spanish Flu"), the most deadly of them all, began in a mild wave and then returned in a far more deadly one. The pandemic of 1957 (or "Asian Flu") began with a mild phase followed, in several countries, by a second wave with higher fatality. The pandemic of 1968 (or "Hong Kong Flu") remained, in most countries, comparatively mild in both its first and second waves. 

Influenza A(H1N1-2009) is a new strain of the flu virus and we lack an in-depth understanding of it.  It is important to be always prepared, by keeping up a high standard of personal hygiene at all times.

It helps to protect people from being infected with the H1N1 influenza virus.

The function of the vaccine is to enable our body’s natural defences, i.e. our immune system, to fight and defend our body against infection by the H1N1 influenza virus.

An immune response that is expected to be protective against 2009 H1N1 influenza virus can be generated within 2 weeks following vaccination.  People who are getting vaccinated should be mindful of this lead time which is needed to build up immunity.

No, you do not need to be vaccinated against H1N1 as your body has already developed immunity against it. However, if your infection was not confirmed through a laboratory test, you may not actually have had the infection. Vaccination is then recommended if you are in one of the target population groups.

Vaccination for seasonal flu does not confer protection against H1N1.

Basically, two different formulations of seasonal influenza vaccaine are made each year. One is for the Northern Hemisphere (NH) winter and the other is for the Southern Hemisphere winter (SH).

It is thus recommended that persons who are vaccinated with the current NH 2009 seasonal influenza vaccine also be vaccinated with the pandemic H1N1-2009 vaccine as this is the predominant circulating influenza strain worldwide currently.  The pandemic H1N1 vaccine and the seasonal influenza vaccine should be administered at least one week apart. 

Whether you should be vaccinated for H1N1 or not depends on your risk profile. Do discuss with your family doctor for his advice.

It is also recommended that persons in high-risk groups who have been vaccinated with the NH 2009 seasonal influenza vaccine and pandemic H1N1 vaccine in 2009 also be vaccinated with the SH 2010 seasonal influenza vaccine when this becomes available in February / March 2010. This is due to a significant difference in the H3N2 vaccine strains between the NH 2009 and SH 2010 vaccines.

It is preferable that the Influenza A(H1N1-2009) vaccine be administered at least 1 week before or after administration of any other vaccine.

The influenza virus may undergo change from year to year.  You are advised to undergo annual influenza immunization with the latest vaccine strains.

The target population groups are people who are at higher risk of developing complications from Influenza A/H1N1 (2009).  They include:

· Pregnant women;
· People with chronic medical conditions (lung disorders, heart diseases, diabetes, kidney failure, neuromuscular disorders); and
· People with chronically suppressed immunity due to disease or long-term medication.
· Young children from 6 months to under 5 years of age.

Healthcare workers and Essential Service Personnel will also be targeted for vaccination first.

Yes, he/she can still be vaccinated. If immediate demand exceeds initial supply, we would advise doctors to give greater priority to the at-risk groups first as they are the more vulnerable groups.

Those who had been confirmed through a laboratory test to be infected with H1N1 do not need to be vaccinated against H1N1.

If you had a severe allergic reaction after a dose of seasonal influenza vaccine, or are allergic to high protein food (like egg or chicken protein), please inform your doctor, who will advise you if you should receive the vaccine.

You should have fully recovered from moderate or severe illnesses before receiving the vaccine.

You could register with your family doctor, Polyclinics or Pandemic Preparedness Clinics (PPCs).  The vaccine will also be made available to other clinics who placed orders with MOH. Click here for list of the Pandemic Preparedness Clinic (PPC). Do give the selected clinic a call before going down  for vaccination.

You should inform your doctor if you:

a.  Have a fever or an infection. (If you have a fever or feeling unwell, you should postpone your vaccination);
b.  Have received any vaccination (whether seasonal flu vaccine or any other vaccine) before;
c.  Have been infected by H1N1 influenza virus before;
d.  Are allergic to any medicines or vaccines, or food (eg, high protein food like egg or chicken protein);
e.  Have other illnesses;
f.  Are taking other medicines;
g.  Are pregnant.

The pricing of vaccination is dependent on a number of factors.  It includes the cost  of the vaccine, distribution, holding of inventory, resources needed for delivery of the injection, and  associated overheads. 

At the polyclinics, their pricing will cover all these costs, without any profit margin.  It is $29 inclusive of GST.

In the industry, GPs and clinics typically factor in the cost of the vaccine by a certain margin to cover all these non-drug/vaccine costs inclusive of a profit margin.

Medisave is primarily for hospitalisation, and cannot be used for vaccination for H1N1.  Patients are advised to visit the polyclinics for H1N1 vaccination if they require financial assistance for H1N1 vaccination. 

The H1N1 vaccine has a similar safety profile as seasonal flu vaccine, which has a good track record. So far, the H1N1 vaccine has not been associated with any unexpected adverse events. General consensus is that any such serious adverse events would be rare. Monitoring on the efficacy and safety of the vaccines is on-going.

Clinical trials to prove the effectiveness of the H1N1 vaccines are ongoing. Initial results indicate that the vaccine is able to produce a strong immune response against the H1N1 virus.

An adjuvanted vaccine has two main components, the antigen (pieces of virus or killed/weakened virus) and the adjuvant.  A non-adjuvanted vaccine only has the antigen as its main component.

An adjuvant is added to a vaccine to improve the immune response and this helps reduce the amount of antigen (pieces of virus or killed/weakened virus) in the vaccine.  For example, a non-adjuvanted vaccine containing 15 mcg of antigen, when added with an adjuvant may need only 7 mcg of antigen to give the same protection to the recipient.  This is known as antigen sparing.

Like drugs, no vaccine is 100 per cent safe. Historically, adverse events to vaccines have been associated with the antigen (pieces of virus or killed/weakened virus) as well as the adjuvant.

To date, there is no conclusive evidence to show that adjuvanted or non-adjuvanted vaccines are more efficacious or safer in the current H1N1 influenza pandemic until they are used on a large scale.

The current H1N1 pandemic vaccine supplied by GSK contains the adjuvant AS03.  An adjuvant is added to a vaccine to help it to work better.

To date, the AS03 adjuvant has been used in 41,000 humans who were vaccinated with other vaccine products containing AS03 and have not shown to cause any safety concern.

You can request to be vaccinated using the Panvax®, CSL, pre-filled single dose H1N1 vaccines. These vaccines do not contain thiomersal.

The side effects may vary from mild to severe adverse reactions, and vary between individuals.  The most common reactions are mild. They include muscle aches, joint pains, headache, fever and soreness or redness at the injection site.  In extremely rare cases, there could be severe allergic reactions, some of which may be life-threatening.

Thiomersal, a commonly used vaccine preservative which contains ethyl mercury, is used in the multi-dose vials of the H1N1 vaccine to prevent bacterial contamination.  Thiomersal contains mercury in a form which does not accumulate in the body. The safety of thiomersal has also been rigorously reviewed by scientific groups. There is no evidence of toxicity in infants, children or adults, including pregnant women exposed to thiomersal in vaccines. The amount of thiomersal in flu vaccines is much less than the daily recommended limit of mercury; for example, a can of tuna fish contains more mercury than the thiomersal in H1N1 vaccines.

Please see a doctor if you experience any of the following:

a.  The side effects persist for more than a few days.
b.  Your fever is high (>38^oC) or persists for more than 48 hours (2 days) despite taking paracetamol.
c.  You have fever accompanied by fits.
d.  You experience severe allergic reactions (or anaphylaxis) where you may feel severe anxiety, itchy skin rash, swelling of the lips and face or difficulty in breathing.

If you feel it is serious you may need to call an ambulance or go directly to a hospital emergency department.

For relief of fever and possible pain from the vaccination, you may wish to:

a.  Take paracetamol. 
b.  Place a cold, wet cloth over the injection site for pain, redness, or swelling.

MOH has ordered 1 million doses of the vaccine and the first batch is expected to arrive on the week ending 7 Nov 2009, with the next batch arriving 2 weeks apart.  Full delivery of the 1 million doses is expected by end of 2009.

Yes, the vaccine is available to all clinics when they place orders with the MOH-appointed distibutor. The initial supplies of H1N1 vaccine will however be allocated first to polyclinics and the PPCs.

All GP clinics including non-PPCs, may wish to make their order as early as possible.  Delivery of vaccines will be rolled out according to this prioritization scheme and the timing of order placement.  Nonetheless, prioritization order for PPC will end on 15 November 2009, after which allocation of order will be the same for both PPC and non-PPC.  Clinics may wish to pre-register their patients who are interested to be vaccinated.

MOH and HSA have reviewed the use of Panvax in children aged 6 months and above and are satisfied with the data on its safety in this age-group. The vaccine is now  available to children from 6 months old at the polyclinics and General Practitioner (GP) clinics (i.e. both Pandemic Preparedness Clinics (PPCs) and non-PPCs). 

Only the vaccine from Panvax®, CSL, which is a non-adjuvanted vaccine, has been approved by the Health Sciences Authority (HSA) for children 6 months and older. The composition of the vaccine for adults and children are the same.

The dosage for children 6 months or older are as follows:

a. For children 10 years and above: Single dose of 0.5 mL (15mcg). This is similar to the current adult dose recommendation.

b. For children from 3 years to less than 10 years: Two doses of 0.5 mL (15mcg), given at least 4 weeks apart.

c.  For children from 6 months to less than 3 years: Two doses of 0.25 mL (7.5 mcg) given at least 4 weeks apart.

As a large number of H1N1 cases had occurred in the younger age groups, we strongly encourage vaccination as they are at higher risk of developing influenza-related complications, especially if they have pre-existing chronic medical conditions e.g. asthma and other chronic lung diseases, heart diseases, epilepsy and other neurological and neuromuscular diseases, kidney diseases, blood disorders or diabetes.

You could register with your family doctor, Polyclinics or Pandemic Preparedness Clinics (PPCs).  The vaccine will also be made available to other clinics that placed orders with MOH. Click here for list of the Pandemic Preparedness Clinic (PPC). Do give the selected clinic a call before going down for vaccination. 

The vaccines are supplied at cost to all polyclinics and GP clinics. The public is advised to check with the clinic on the pricing of the vaccine as charges may differ due to differences in administration, inventory and overhead cost of the vaccines. Patients who cannot afford the vaccine can seek assistance from the polyclinics. No one will be denied essential vaccines because of their inability to pay.

The following groups of children should not be vaccinated against H1N1:
a. Those with severe allergic reactions after a dose of seasonal influenza vaccine, or are allergic to high protein food (like egg or chicken protein). They should consult their doctor who will advise them accordingly regarding vaccination.
b. Those who have been confirmed through a laboratory test to have been infected with H1N1. These children have already developed immunity against the virus and so do not need vaccination.

The possible side effects experienced by children are similar to adults. The H1N1 vaccine has a similar safety profile as the seasonal influenza vaccine. So far, the H1N1 vaccine has not been associated with any unexpected adverse events.

The possible side effects vary from mild to severe. The most common reactions are mild, including muscle aches, joint pains, headache, fever and soreness or redness at the injection site. In extremely rare cases, there can be severe allergic reactions, some of which may be life-threatening.

Please see a doctor if you observe any of the following:

a. Any side effects persist for more than a few days.
b. There is high fever (>38°C) or fever which persists for more than 48 hours despite taking paracetamol.
c. Fever accompanied by fits or seizures.
d. Severe allergic reactions (anaphylaxis) which may manifest as severe anxiety, itchy skin rashes, swelling of lips and face or difficulty in breathing.

You may need to call an ambulance or proceed directly to a hospital emergency department if the reaction is serious.

If there was no confirmation that your child was infected with H1N1, he/she can be vaccinated. However, a doctor should be consulted in order to assess his/her condition and decide on an appropriate time for vaccination.

It is preferable for the vaccine to be administered at least 1 week before or after administration of any other vaccine.

Although H1N1 vaccination can help protect your child against the H1N1 virus, it is important to continue to inculcate good personal hygiene habits.

• Teach your child to wash hands frequently and thoroughly with soap and water.  If soap and water are not available, an alcohol-based hand sanitizer is also adequate.
• Keep your child, if he/she has flu-like symptoms, at home until he/she has fully recovered.
• Instruct your child not to share drinks, food, or personal items like pencils or clothing at school or daycare.
• Teach your child to cover his/her mouth and nose with a tissue paper when coughing or sneezing and to dispose the used tissue in the dustbin.

If you live with or care for children younger than 6 months of age or children who have high risk medical conditions, it is advisable that you also go for H1N1 vaccination.

Studies of H1N1 vaccination in pregnant women are ongoing. However, studies in experimental animals using non-adjuvanted or adjuvanted vaccines found no evidence of direct or indirect harmful effects on fertility, pregnancy or development of the embryo or fetus. Based on these data and the significantly increased risk in pregnant women infected with the pandemic virus, vaccination may be considered during the second and third trimester.

Due to the longer track record of safety of the non-adjuvanted vaccines for pregnancy in general, it is recommended that non-adjuvanted vaccines, if available (e.g. Panvax ®, CSL) should be used instead of adjuvanted vaccines for this group of patients. You may wish to discuss further with your doctor / obstetrician should you wish to be vaccinated. 

Yes. Breastfeeding mother can receive both the seasonal and Influenza A (H1N1-2009) vaccine (but should be administered at least one week apart).  Vaccination of breastfeeding mother can prevent the flu in mothers and reduce the infant's chances of being infected with the flu. In addition, breastfeeding allows mothers to pass on to the infant the antibodies that their bodies make in response to the vaccines, which can reduce the infant's chances of getting sick with the flu.

The symptoms of influenza A (H1N1-2009) in people are similar to the symptoms of seasonal influenza. An early symptom is high fever, and this is followed by cough, sore throat, runny nose, and sometimes breathlessness a few days later. 

Oseltamivir (Tamiflu®) or Zanamivir (Relenza®) are antiviral drugs that can be used to treat Influenza A (H1N1 -2009) infection.  As with any other medication, there are potential side effects related to the use of Tamiflu.  We would advise that individuals see a doctor early if they are feeling unwell rather than to self-medicate.

MOH has built up a national stockpile of antiviral drugs for treatment which is sufficient for those who are living in Singapore.

Tamiflu is not available over the counter as it is a prescribed drug.  It can only be sold as a prescribed drug by a hospital or medical centre and not available to be purchased from the retail shelves.

As with any other medication, there are potential side effects related to the use of Tamiflu.  We would advise that individuals see a doctor early if they are feeling unwell rather than to self-medicate.

Tamiflu can be considered for all children above 1 yr of age, especially if they have high-risk conditions that makes the influenza disease more complicated including asthma. 

There is inadequate data about the safety of Tamiflu for infants under 1 year, so parents need to be counselled.

The most frequent side effect reported in children and adolescents admitted to KK Hospital for Influenza A (H1N1-2009) and treated with Tamiflu is nausea. However, this was usually observed after the first dose of Tamiflu and improved with subsequent doses.

Although less common, a small number of patients have shown neuropsychiatric symptoms such as anxiety and panic attack, The symptoms included agitation and panic attack, disorientation and suicidal ideation. However, these symptoms may not necessarily be caused by Tamiflu as influenza infection and a high fever can also cause some of these symptoms.

As a precautionary measure, caregivers of young patients should be on a look out for the remote possibility of abnormal behaviour while on Tamiflu treatment. If abnormal behaviour is noted, they should seek medical attention as soon as possible.

Tamiflu can be given to patients with asthma.

The decision to treat pregnant and/or breast-feeding mothers with Tamiflu will be determined by their doctors.  Antiviral medicines are used only when the potential benefits to the mother justifies the potential risk to the foetus or child.

If a dose of the antiviral medicine has been missed, patient should not double the next dose.  Instead, the patient should take the missed dose as usual as soon as he remembers to do so.

However, if it is near the time for the next dose of antivral medicine, skip the missed dose altogether.  A double dose of antiviral medicine should not be taken because this may increase the risk of adverse or unwanted effects.

Practise good personal hygiene and be socially responsible by:

a.  Washing your hands regularly and thoroughly with soap and   water, especially before touching your eyes, nose or mouth;
b.  Turning quickly away from anyone near you if you are about to cough or sneeze, and do not cough or sneeze at him;
c.  Covering your nose and mouth with a tissue when coughing or sneezing. Dispose of the tissue properly in the dustbin after use;
d.  Avoiding crowded places if you are unwell and wear a surgical mask to cover your nose and mouth;
e.  Staying home from work or school when you are sick; and
f.  Using a serving spoon when sharing food at meal times.

In addition, leading a healthy lifestyle helps to build up your immunity and protects you against infection.

a.  Eat a balanced diet, including plenty of fruit and vegetables.
b.  Be active. Do 30 minutes of physical activity at least 5 days a week.
c.  Learn to relax and have enough sleep and rest.
d.  Do not smoke.

Soap and water or commercially available alcohol rubs with appropriate hand hygiene protocol can be used. Soiled hands, however, will need to be cleaned with water and detergent before the use of alcohol rub.

Yes, scientific studies have shown that hygienic measures such as regular hand washing with soap and water can prevent the spread of respiratory viruses (including influenza) in the community.

Environmental surfaces should be washed/wiped with 1:50 diluted household bleach (i.e. adding 1 part of bleach to 50 parts of water) immediately. Metallic surfaces can be cleaned with 70% alcohol. Soiled surfaces should be cleaned with water and detergent before applying alcohol and bleach.

Surgical masks are designed to prevent the wearer from spreading respiratory droplets but cannot stop him from breathing in small particles.

A respirator mask such as N95 is designed to protect you from breathing in very small particles which might contain viruses. To work effectively, N95 respirator masks must be specially fitted for each person who wears one (called "fit-testing").
 
Surgical masks are loose-fitting disposable masks that should cover the nose and mouth. Small facemasks are available for use by children. Refer to the Influenza A (H1N1-2009) webpage (http://www.moh.gov.sg/mohcorp/influenzah1n1/) for steps of putting on a surgical mask.

If used correctly, masks and respirators may help reduce the risk of getting influenza, but they should be used with other preventive measures such as avoiding close contact and maintaining good hand hygiene. A combination of actions is needed, as no single action will provide complete protection

Influenza virus spread easily from person to person mostly through coughing and sneezing by large droplet secretions. Close contact (within 2 metres) with someone ill with influenza carries an increased risk of infection. More crowded conditions increase the chance of being exposed to infectious material (e.g. from coughs and sneezes).

We would like to encourage a culture of staying home when one is down with flu.  Wearing a surgical mask can be considered if you are sick with flu and think you might have close contact with other people.

The correct steps to put on and dispose of a surgical mask are illustrated here.

The proper steps to remove a pair of used gloves are illustrated here.

Educational resources are available on the following sites:

MOH website - At the left hand pane, please select 'For the public - Resources'

HPB website - At the top pane, please select 'Educational Materials'

Flu site - At the left pane, please select 'Resources'

The Health Information Centre of Health Promotion Board has educational materials for the public on healthy living.  You may wish to contact them at 6435-3954, or email to them at HPB_HIC@hpb.gov.sg for more information.