Influenzanet is a system to monitor the activity of influenza-like-illness (ILI) with the aid of volunteers via the internet

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Developing the framework for an epidemic forecast infrastructure.

The Seventh Framework Programme (FP7) bundles all research-related EU initiatives.

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Participating countries and volunteers:

The Netherlands 11953
Belgium 3946
Portugal 1747
Italy 4295
Great Britain 4159
Sweden 3559
Germany 184
Austria 506
Switzerland 678
France 6236
Spain 996
Ireland 295
Denmark 1309
InfluenzaNet is a system to monitor the activity of influenza-like-illness (ILI) with the aid of volunteers via the internet. It has been operational in The Netherlands and Belgium (since 2003), Portugal (since 2005) and Italy (since 2008), and the current objective is to implement InfluenzaNet in more European countries.

In 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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2016/17 Flusurvey Results

This report describes the final analysis of the 2016/17 flusurvey which commenced on the 2nd of November, 2016 (week 44) following established influenza circulation and was completed on 7th of May, 2017 (week 18). It forms part of the routine surveillance duties carried out by Public Health England (PHE) to monitor the burden of influenza-like-illness in the community using non-traditional surveillance methods. In total, 4,137 individuals registered to participate in the weekly survey of which 4,040 (97.7%) completed at least one symptoms survey questionnaire suggesting a high engagement rate with its users. During the survey period, 52,332 real-time flu related symptoms data were reported, figure 1 shows the distribution of registered participants and those completing the weekly symptoms questionnaire up to and including week 18 which indicates an average response rate of 60.0%.
Figure 1: Number of registered participants compared to those completing the symptoms survey each week up to week 18, 2016/17
The cumulative influenza-like-illness clinical attack rate among active participants (those who completed at least 3 symptoms questionnaire) over the survey period was 3.3%. The weekly incidence rate by age group is presented in Figure 2 and shows peak ILI activity among participants in week 52. On average, the <20 years old age group reported higher ILI for the most of the survey period. These findings were not consistent with the PHE influenza surveillance data, which showed that the highest disease burden was reported in the 65+ age group with influenza A(H3N2) being the dominant circulating strain in 2016/17.
Figure 2: FluSurvey Overall ILI incidence and by age group, UK - up to week 18, 2016/17

Characteristics of Flusurvey Participants

There were 4,040 participants who completed at least one week's symptoms questionnaire during the survey, 65.3% of whom were women (Figure 3). The mean age of participants was 48.7 years higher than last season which was 42.7 years. The age distribution of respondent was not representative of the national average estimates (Figure 4), as the survey suggested more people aged 35 years and over; classified as highly educated and in full employment were more likely to sign up and participate in the survey. Increasing the number of households with children (only 5.0% of participants were <18 years old) participating in the survey is important to enable us better understand the dynamics of influenza transmission within this population given that children are known disease drivers

Figure 3: Gender distribution of participants, week 42 2016 to week 18 2017
Figure 4: Age Group of participants with national estimates, 2016/17
Figure 5: Employment status of respondents, 2016-17
Figure 6: Mode of transport of participants, 2016-17

More than half (57.6%) of survey participants reported using their car as their main mode of transportation compared to public transport (21.3%) or walking (14.2%)

Figure 7: Where do Flusurvey participants come from?

Figure 7 shows which region Flusurvey participants reported they reside. The highest number of respondents lived in the South East and London region and were very well represented in the survey. However, only a hand full of respondents were living in Isle of Man, Channel Island and Northern Ireland. We will be exploring ways to engage more people to register and participate in the survey in the coming season

Figure 8: Most commonly reported flu symptoms, 2016-17

Above you can see the most commonly reported symptoms amongst cases during the flu season. Sudden onset of symptoms and runny nose were the most frequently reported symptoms while chest pain and fever were least amongst Flusurvey participants.

Figure 7: Weekly ILI rates by age groups in 2015/16, results up to week 20

Data up to week 20 shows that ILI incidence per 1,000 among flusurvey participants peaked at week 8. The highest ILI incidence was observed among 0-19 year olds. 

Note: data for wk 7 is an average of data collected in wk6 and wk8 since no data was available
Figure 8: Weekly ILI incidence per 1000, 2015/16
Figure 9: The reasons respondnents gave for receiving or not receiving the 2015/16 flu vaccine.

1775 (43.3%) participant reported receiving the 2015/16 influenza vaccine. The reason participants gave for receiving or not receiving the flu vaccine are presented in the figure above. Encouragingly, a relatively small proportion of people had negative attitudes about the influenza vaccine (i.e. concerns around safety, side effects or efficacy of vaccine) while increasing vaccine availability and improving convenience of administration (e.g. in the work place) would increase vaccine uptake in the general population.

Figure 10: Healthcare seeking behaviours reported by participants, 2015/16

This figure above shows the proportion of Flusurvey participants reporting a flu-like illness in the 2015/16 flu season and who sought care from a health professional either by calling a service or visiting, or what medication they may have taken. It is important to note how the proportion of participants who reported taking painkillers were similar to that of those who did not seek healthcare services.