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What is influenza A (H1N1-2009)?
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.
What is the incubation period of Influenza A (H1N1-2009)?
The incubation period for the virus is estimated to range from 1 to 7 days.
Why are MOH and other public health authorities such as the World Health Organisation (WHO) and the US Centers for Disease Control and Prevention (CDC) concerned about influenza A (H1N1-2009)?
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. Unlike seasonal influenza, there is no vaccine available yet. It will take several months for scientists to produce a vaccine for this new strain of H1N1 virus. There is also concern about how many people will turn out to develop serious illness due to this new strain. If many people develop serious illness, healthcare systems will be overloaded.
How does influenza A (H1N1-2009) spread from humans to humans?
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.
If a patient had recovered from the Influenza A (H1N1-2009) virus, can he/she be infected again with the Influenza A (H1N1-2009)?
The Influenza A (H1N1-2009) is a new virus strain, and the implications of this phenomenon are unknown. In general, infection with influenza viruses can generate antibodies which are protective against future infection by the same virus strain. However, if the specific virus undergo significant mutation, it is possible to be infected by the mutant strain.
Is the case-fatality rate Influenza A (H1N1-2009) much higher than other flu strains?
Case fatality rate (CFR) is the proportion of people with a disease who will die. The case fatality rate for the Influenza A (H1N1-2009) infection remains unclear. Initial reports from Mexico cited a high case-fatality rate (ie in excess of 5%, which is higher than even the Spanish flu of 1918). However, the case fatality rate is lower, at 0.16% for cases of deaths outside Mexico. The virus strain in Mexico appears identical with that found in the US and hence, the actual case fatality rate in Mexico might have been lower.
The latest study from WHO estimates that up to 32,000 may have been infected in Mexico, and case fatality rate is estimated at 0.4% (with a range of 0.3% to 1.5%). North America suggested a case fatality rate of 0.37%. The virus, like other flu viruses, is also constantly changing. New mutations may be harmless versions of itself but there is also the possibility that the virus may become more infectious and lethal. It will take time for the full picture to emerge.
What is the impact of Influenza A (H1N1-2009) being a mix of several strains of the flu virus?
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.
How can human infections with Influenza A (H1N1-2009) be diagnosed?
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.
What kind of waves can we expect for Influenza A (H1N1-2009) if it becomes a pandemic?
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 still too early to predict how exactly it will act and if or when another wave might hit. Hence, it is important to be always prepared, by keeping up a high standard of personal hygiene at all times.
Symptom, Treatment & Vaccination
What are the symptoms of Influenza A (H1N1-2009) in humans?
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.
What medications are available to treat Influenza A (H1N1-2009) infection in humans?
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.
Should people purchase and carry Tamiflu, so they can take it the moment they feel the flu is coming on?
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.
Are there enough stockpiles of antiviral drugs in Singapore?
MOH has built up a national stockpile of antiviral drugs for treatment which is sufficient for those who are living in Singapore.
Should the public get vaccinated against flu?
Flu vaccination helps protect against flu by building up the body’s immunity against flu virus. Yearly vaccination is recommended for groups at higher risk of complications of influenza, such as:
1. Persons aged 65 years and older;
2. Children who are 6 months to 5 years;
3. Adults and children who have chronic diseases such as asthma, diabetes, or kidney failure on dialysis;
4. Women in the second or third trimester of pregnancy
In addition, to prevent transmission to persons identified above, influenza vaccination is recommended for healthy household contacts and caregivers of children aged 5 years and below, and persons at higher risk of complications of influenza, and for healthcare workers.
However, flu virus changes rapidly and every year different strains of virus become predominant, vaccines need to be reformulated every year.
Does influenza vaccination help in preventing influenza A (H1N1-2009)?
It is not known whether the current seasonal flu vaccine protects against Influenza A (H1N1-2009) strain. Some patients with Influenza A (H1N1-2009) have been reported to have been previously vaccinated with the seasonal flu vaccine. This may mean that the seasonal vaccine is not protective, but because flu vaccine is never 100% protective anyway, we cannot be absolutely sure.
There is no vaccine available for Influenza A (H1N1-2009) yet. Vaccine manufacturers will be producing a vaccine for this new strain of virus.
Source: Ministry of Health, Singapore
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