Influenzanet is a system to monitor the activity of influenza-like-illness (ILI) with the aid of volunteers via the internet
Developing the framework for an epidemic forecast infrastructure.
http://www.epiwork.eu/
The Seventh Framework Programme (FP7) bundles all research-related EU initiatives.
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4444In contrast with the traditional system of sentinel networks of mainly primary care physicians coordinated by the European Influenza Surveillance Scheme (EISS), InfluenzaNet obtains its data directly from the population. This creates a fast and flexible monitoring system whose uniformity allows for direct comparison of ILI rates between countries.
Any resident of a country where InfluenzaNet is implemented can participate by completing an online application form, which contains various medical, geographic and behavioural questions. Participants are reminded weekly to report any symptoms they have experienced since their last visit. The incidence of ILI is determined on the basis of a uniform case definition.
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Measuring influenza-like-illness
When are flu-like symptoms really flu?
The only definitive way to say if someone has flu is by testing a swap for presence of the virus in the laboratory. This is impractical for diagnosing lots of people because it takes time and resources. Instead, GPs and health researchers use a combination of common symptoms as a working definition of flu. The most common symptom of flu is a fever that came on over a couple of hours, however different flu strains may cause a different combination of symptoms, and different people might be more or less prone to developing particular symptoms. In the flusurvey, we ask about:
- Fever
- Chills
- Bloodshot eyes
- Runny nose
- Sneezing
- Sore throat
- Cough
- Headache
- Muscle pain
- Chest pain
- Tiredness
- Vomiting
Even with a list of symptoms measuring flu in the community is not simple - there are plenty of infections around that can look like flu, and plenty of people with flu who do not display the 'classical' symptoms.
In addition to that, different public health bodies use different combinations of symptoms to diagnose 'influenza-like illness' (ILI).
In America, the Centre for Disease Control defined swine flu-like illness as 'Fever plus cough plus headache plus any of the following symptoms runny nose, blocked nose, joint pain, muscle pain, weakness, sore throat, chest pain, abdominal pain, nasal congestion'.
Whereas in the UK, the Health Protection Agency defined swine flu-like illness as 'Fever plus two or more of a cough, sore throat, runny nose, joint pain, headache, vomiting or diarrhoea'.
That means that someone with a fever, sore throat and runny nose would be diagnosed with ILI in the UK but not in the USA.
During the 2009 epidemic, we analysed how applying different definitions of ILI effects how big we think the epidemic is. The figure below shows what happens when we apply these different measures to information provided by flusurvey users.
One problem is that the definition really ought to change from week to week, depending on what other infections are around (in the summer, most things that looked a bit like flu probably were flu, whereas in the winter there are lots of other infections cropping up too) - this might be too much of a challenge, but it'll keep us busy during the coming season.
