Results Summary 2011

Thank you for participating in Flu Watch. Here are some of our findings so far from the information you have provided to us since October 2010.

Weekly Illness Data

This is the fifth year we have collected weekly illness data over the flu season. The graph below shows the rates of influenza-like illness reported to Flu Watch in the last three influenza seasons. You have an ‘influenza-like’ illness when you have a temperature of 37.8°C or above, as well as a cough or sore throat.

As you can see, we collected some extra data over the summer of 2009 due to the pandemic. This year’s rate of flu-like illness in Flu Watch participants is shown by the green line. Interestingly, at its peak there was more flu-like illness this winter than during the pandemic last year. The highest rate of flu-like illness was seen in 2008/9 when a different type of flu virus was circulating (see the pie-charts below).

2010-11 Results Graph

Who got ill?

This flu season (October 2010 onwards) older adults aged 65 and over have reported the lowest rate of influenza-like illnesses. They had ten times less influenza-like illness than 0-4 year olds, and 6 times less than 5-15 year olds. They had half as many influenza-like illnesses as 16-44 year olds.

Strains of circulating influenza virus.

There are usually several strains of flu circulating over the winter. These strains vary each year, so a new vaccine is released every autumn to protect against the strains around that year.

There are two main types of influenza virus, influenza A and influenza B. While there is only usually one type of influenza B virus, there can be several sub-types of influenza A circulating each year. These are what you hear about on the news when they’re talking about H1N1 or H3N2, and these sub-types vary year-to-year.

We’ve asked our participants over the last five years to send us nasal swabs when they were ill, allowing us to investigate whether they had a viral infection and if so what type of virus they were infected with.

Between 83-93% of the swabs you sent had no detectable virus on them. The graphs below show the proportions of different strains of viruses that we found on the positive nasal swabs in each year of the study. You can see that H3N2 (dark blue) was circulating in the first three winters, but hasn’t been seen within Flu Watch in the last two winters. Likewise the H1N1 seasonal strain (red) has disappeared since the H1N1 pandemic strain (green) started to circulate.

2010-11 Results Graph

We will soon be getting your blood results back, and so will be able to see who was infected with influenza virus this year by looking at your immune response.

We are also currently writing the results up for publication in a scientific journal and will post links to those articles online when they are available.

Thank you again for the time and effort you have put in to participating in Flu Watch.


Flu Watch 2009-2010 Results Summary

Flu Watch answers important questions

Here are some of the questions Flu Watch has been able to answer thanks to the participation of our study members.

How common is flu?

Although many people say that they very rarely get flu the study shows that every year around 15 -20% of people are infected. Children are the most likely to be infected and the elderly are the least likely.

Does flu infection always make you ill?

Did you know that you can get infected with the flu virus but only have very mild illness or no illness at all? Many people with evidence of flu infection from their blood tests reported only mild symptoms or no respiratory illness at all.

What symptoms does flu cause?

Flu is often hard to tell apart from other common infections. A temperature of over 37.5 decrees Celcius, feeling feverish, headache and muscle aches are all more common in flu than in other common respiratory infections …. but lots of people with other infections can get these symptoms too ….and many people with flu do not have these symptoms! That is why it is important for Flu Watch participants to send in nasal swab samples for all their respiratory illnesses not just ones they think are flu.

Why do some people feel very ill whilst others stay well?

We don’t know the answer to this question yet but we are hoping that continuing detailed analysis of participant’s immune response will give us the answer. We are very grateful to all participants who have provided blood specimens to help answer this question.

Did more people than usual get ill during the 2009 influenza pandemic?

The graph below shows weekly Flu Watch reports of flu like illness (blue bars) and laboratory confirmed disease from nasal swab tests (red line). You can see that the amount of flu like illness and confirmed cases reported during the pandemic (2009/10) were similar to other years.

2009-10 Results Graph

So why all the fuss about pandemic flu?

Whilst normal flu causes death mainly in the elderly the new flu strain killed mainly young people. Most of those who died had underlying illnesses but some of the deaths were in previously healthy people. In the UK it was estimated that during the pandemic around 1 in 2000 cases died although our data suggest the true figure is probably lower than this.

How many people used antivirals?

During the pandemic antivirals were made available to anyone with symptoms of influenza. Our information shows that most people with flu used simple cold and flu remedies from the chemist rather than getting antivirals. Only a small proportion of confirmed flu cases were treated with antivirals.

Did the “Catch it, Bin it, Kill it” campaign work?

More Flu Watch participants reported covering their mouth when sneezing, throwing away dirty handkerchiefs, and washing their hands after sneezing than before the pandemic. This suggests the campaign did help to change behaviours.

How can I protect myself against flu?

If your doctor recommends that you have flu vaccine then taking up the offer will help protect you. Flu vaccine is recommended for the people who are most likely to get severely ill from flu. The main groups are those aged 65 or over, those with long term illnesses and pregnant women. Health care workers are also recommended vaccine to protect themselves and to help stop them spreading flu to their patients. Flu Watch results shows that people who wash their hands regularly have a substantially lower risk of flu. This suggests that a lot of people catch flu by touching their mouth, eyes or nose with contaminated hands. We found men were less hygienic than women and of course children were the least hygienic. We’ll let you draw your own conclusions!

What happens to the information you get?

All of our participants’ information is kept securely and only the core study team have access to names and addresses. When we analyse the results we make sure the main findings are shared with relevant committees so that they can help to influence government flu policy. We have also presented results at conferences nationally and internationally to make sure that other scientists can learn from the findings. We plan to publish results in scientific journals shortly.

Why do we need to continue Flu Watch?

Flu Watch is one of very few studies across the world that can tell us about who really gets ill with flu because most people with flu don’t go to the doctor. Although we have already found out a lot about flu – we still want to find out more. The more information we have the more questions we can answer. This year nobody knows yet whether the 2009 pandemic strain will still be the main strain or whether more familiar seasonal strains will return, or perhaps there will be another new strain that we hadn’t expected. With the help of our participants we will keep watching what happens.