I saw my first case of flu for the season last week.
When I say this I actually mean that I saw the first person with symptoms severe enough to make me think they might have THE flu. That is, they are infected with an influenza virus, rather than another virus. People often tell me they have ‘a flu’, usually meaning they have a cold. Colds are caused by other types of virus, of which there are many, and they can make you feel dreadful too.
However the reason we are all so interested in influenza is that left unchecked it can be a huge killer. That is because, compared with most cold viruses, someone with influenza is more likely to get a complicating severe illness (eg. pneumonia), and because influenza causes epidemics.
It has the ability to change (mutate) over time, so as fast as our bodies develop immunity to one influenza virus, another one with slightly different proteins on it’s surface emerges. It is the proteins that trigger our immune system to respond, so when they change we have to start (at least partly) over again learning to recognise the new ones. And while we are doing that the virus is wreaking havoc in our bodies, whereas if we already had immune cells ready to go the virus could be dealt with sooner after it’s arrival in our noses/lungs.
There are 2 main groups of influenza viruses which make humans significantly unwell: Influenza A can also infect animals; influenza B can only infect humans. Within those divisions there are multiple sub-types, which have been classified according to the types of (glyco)proteins on their surfaces: H (haemagglutinin) and N (neuraminidase). Which is why a strain of influenza will be described as H5N1, H1N1 etc.
Vaccination is a way of introducing your body to the virus proteins: Enough to allow it to prime some immune cells in preparation for a real attack. You can feel mildly ‘under the weather’ while the chemicals involved in preparing immune cells are doing their job in your body. But you will not catch influenza from it – there are no live viruses able to reproduce in any of the vaccines. You can however catch a cold at that same time, particularly since flu jabs are given at a time of year when all the cold viruses are getting going too, and the flu jab doesn’t protect against those – they have different surface proteins.
Immunology is an incredibly complex, and evolving, area of study. The effect of the same Influenza virus, on 2 people, will be different because the way their bodies work is different, making it hard to predict who will be seriously affected. Vaccination helps, it gives the body a head-start, but just occasionally that isn’t enough to fully prevent illness, and of course some of the population can’t be vaccinated against influenza. So the less likely you are to come across the virus the better. That is where the hand washing, ‘catch it, bin it, kill it’ and herd immunity come in. We will talk more about herd immunity next month, but suffice it to say for now that if you are lucky enough to be able to have a flu jab it will protect not only you, but every person that you know, that they know, that they know, and so forth. Indirectly you will be preventing serious illness in people who are unable to have the vaccine, like children on chemotherapy or babies under the age of 6 months.
I’ve booked myself in for my flu jab this month, because I want to look after myself, my family and my patients, but also because I’m doing my part to protect vulnerable individuals that I will never even meet. I won’t be forgetting to wash my hands regularly, or to remind my children to ‘catch it, bin it, kill it’ either, helping improve our chances of avoiding not only flu, but all the circulating cold viruses and stomach upsets.
Until next month – stay well.
By Dr Kate Roberts
You can read more about the DHU Health Care Flu campaign by following the link.