Dating the emergence of pandemic influenza viruses

Questions and answers on influenza pandemics

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Influenza viruses are coated with two proteins, called haemagglutinin HA and neuraminidase NA. There are many subtypes of influenza A with different variants of haemagglutinin and neuraminidase, although most of these subtypes only circulate in birds. Influenza B viruses only infect humans and are not classified into subtypes.

In addition to "antigenic shift", the haemagglutinin and neuraminidase of type A and B viruses continually change by mutation to produce new strains of the virus, a process referred to as "antigenic drift". Can I build long-term immunity to influenza? Infection with influenza virus, or immunisation, induces the body to produce antibodies to the strain s of virus encountered. Antibodies against the haemagglutinin are the most important for protecting us against influenza virus infection.

Dating the emergence of pandemic influenza viruses. - Semantic Scholar

As the circulating viruses change by mutation these antibodies become less effective at neutralizing the virus and within a relatively short time they are no longer protective. Therefore infections can occur repeatedly throughout life and protection by vaccination requires annual dosing with updated vaccines. When a new subtype of influenza A emerges, most of the population is highly susceptible and infection rapidly spreads worldwide, producing a pandemic. Treatment of Influenza Can influenza be treated?

There are two forms of treatment for influenza, symptomatic and antiviral. Drugs that lessen the symptoms of the disease, such as a runny nose, high temperature, coughs and headache, are available over the counter in pharmacies and sometimes supermarkets: Other drugs that limit the multiplication of the virus are generally only available by prescription from a doctor.

This second group comprises the drugs known as 'neuraminidase inhibitors', zanamivir Relenza and oseltamivir Tamiflu which act on both influenza A and B, and the older drugs Amantadine and Rimantadine. Amantadine and Rimantadine are no longer recommended as currently circulating influenza strains have developed resistance to this class of drugs. Not all anti-viral drugs are available in all countries. Vaccination against Influenza How can I protect myself from flu? Yearly vaccination is the best way to protect yourself from seasonal influenza infection.

What happens during a pandemic — how do health services and hospitals cope? One earlier planning estimate of the additional stress that a European health service caring for people might experience over the first wave of a pandemic is as follows: However, perhaps the same proportion might be off because they were caring for someone else who is in the family.

This is only one estimate undertaken for planning and there are others estimates that can be made which will look worse or better. That is why you can read different guesses at the number of people who will die early in a pandemic. But in a real pandemic the pattern will always be more complicated.

With these kind of numbers health services come under stress during a pandemic. Primary care can be stressed additionally by people who are anxious and seeking reassurance or if it is decided to make antivirals available to everybody who becomes unwell. This can be made even worse by staff who will be off sick themselves or caring for others.

That is why planning is so important and fortunately health services in many countries do such planning all the time, planning what they will do with different crises, major accidents, bombs going off, etc.

However a pandemic is especially difficult because it runs on and affects all the health services in every part of the country. But pandemics have been planned for in every European country to greater or lesser extents.

What happen during a pandemic — are other services affected beyond the health services? Certainly one as bad as would affect services.

However again that is why planning for a pandemic is not just in the health services. Are all pandemics the same? Pandemics do not come in a standard size. Of the three pandemics that took place in the 20th Century, those of and were were roughly as severe as each other in terms of the numbers of additional deaths attributed to them but they still differed considerably in their other characteristics for example the most affected groups. When will the next pandemic take place, and which virus will cause it?

We simply do not know and there is no way of knowing. An influenza pandemic could start this winter, it could start next summer or it might not happen for more than five or ten years from now. Influenza viruses are inherently unpredictable. This is work underway now to determine which of the animal viruses are more likely to undergo pandemic change and which should be prepared for.

But this is certainly not a matter of making predictions. How do influenza pandemics start? We do not know for sure. Theoretically there are at least three ways this could happen: They then exchange genetic material and produce a new reassortant virus that is new to man. A second possibility is of a strain of animal influenza changing and becoming able to infect humans and transmit among them. A third theoretical scenario is of an existing human influenza mutating into a new virus type.

Dating the emergence of pandemic influenza viruses.

Why has there been so much concern about the bird flu outbreaks involving A H5N1? Firstly this strain is persisting among domestic poultry in a number of countries where poultry and human are in close contact, therefore there is a constant risk or humans being infected and the virus adapting to them.

Secondly this virus has already shown the ability to infect and adapt to a number of quite different bird species, which is unusual. But the longer it is around, the more potential there is. What is therefore especially worrying is that H5N1 is now deeply embedded in poultry in a number of countries despite many attempts to eradicate it there.