Each country is coloured by how its most recent ILI/ARI rate compares to its own history for the same week of the year — not to the raw numbers other countries report. The five bands (very low → very high) share the ERVISS band names but are locally computed percentiles, not MEM thresholds.
The ERVISS feed mixes two denominators: some countries report per 100 000 population, others per 100 000 consultations. Same disease, same week, no flag in the file to tell them apart — Austria's 2817 and Iceland's 5.5 are not on the same scale. Banding each country against itself sidesteps this.
ILI is heavily seasonal, so a plain all-history percentile would just paint the map by month. The bands here compare against the same ISO week in each of the previous 8 seasons — answering "is this week high for this time of year?".
2020, 2021 and 2022 are explicitly excluded from the reference distribution. Consultation patterns during and immediately after COVID-19 were so distorted (behavioural change, sentinel-network drop-out, definition changes) that including them drags the "normal" baseline into a range that isn't normal at all — a country's ordinary winter would then look unusually high. Excluding those years and widening the window to 8 seasons gives a cleaner sense of what a genuine anomaly looks like. Where a country's ERVISS series is short, seasons_used in the tooltip flags how thin the evidence is.
The band says the current value is unusually high for that country at that week. It cannot distinguish a genuine surge from a change in how that country counts (denominator switch, sentinel-network change, reporting-cadence shift). Treat a lone very-high country as a signal to check the source, not as a comparative claim against its neighbours.
As a partial safeguard, values that sit well beyond the country's own historical range for the same week (more than ~2.5× its 98th-percentile) are treated as likely source-side artefacts and greyed rather than banded very-high.
Source: EU-ECDC ERVISS weekly data. Bands are computed by this site's extractor; see the JSON's band_config field for the exact thresholds.
The US layer shows CDC's ILINet: ~4,000 sentinel outpatient providers report weekly visits meeting the ILI syndrome definition — fever ≥100°F (37.8°C) plus cough and/or sore throat — as a percentage of all outpatient visits (weighted ILI, or wILI).
ILINet is a syndromic count: cases are recorded by clinician observation, not by influenza testing. Since October 2021 the definition also no longer excludes "known cause other than influenza", so ILINet captures anything presenting with those symptoms — influenza, COVID-19, RSV, common cold, other respiratory viruses. A high wILI reading means "more people are turning up with fever + cough/sore throat", not "more people have flu".
Japan reports clinician-diagnosed influenza specifically (usually rapid-test-supported); the US count is syndromic ILI from any cause. A US "low" and a Japan "low" are not the same signal.
Unlike the UK's population-based rate, this is a care-seeking denominator — so raw values aren't comparable across layers.
Each state is coloured by its wILI against the same ISO week in the previous 8 seasons, with COVID-era years (2020–2022) explicitly excluded so pandemic and immediate-recovery reporting doesn't skew what "normal" looks like (percentile cuts p50 / p75 / p90 / p98). Grey = reporting but no meaningful seasonal reference. States reporting more than 4 weeks behind are dropped (currently ~8, through the summer trough).
Source: CDC ILINet via the Delphi Epidata API (Carnegie Mellon University); ILINet is a programme of CDC's US Influenza Surveillance System. Bands are computed by this site's extractor; see the JSON's band_config field for the exact thresholds.
The Japan layer shows JIHS (formerly NIID) IDWR sentinel surveillance: ~500 designated sentinel clinics report weekly clinician-diagnosed influenza as cases per sentinel (定点当たり報告数).
The case definition is influenza-specific: (a) sudden onset, (b) fever >38.0°C, (c) upper respiratory symptoms (cough, sputum, breathlessness), and (d) general fatigue — OR strongly suspected via laboratory diagnosis such as rapid antigen testing. Rapid antigen tests are used very heavily in Japanese clinics, so the reported influenza cases are usually RIDT-supported. They are not PCR-confirmed, but they are flu-specific — this is a narrower, more influenza-specific signal than the syndromic ILI counts the UK and US layers report. A Japan "low" and a US "low" are not the same signal.
Each prefecture is coloured against its own same-week history (percentile cuts p50 / p75 / p90 / p98). To match the other layers, the reference distribution deliberately excludes 2020–2022 so COVID-era distortion can't set the definition of "normal"; JIHS's weekly CSV feed only starts in 2023 anyway, so the exclusion doesn't remove anything today but keeps things clean if the pre-2023 archive is ever back-filled. History is currently 2–3 seasons — during the summer trough most prefectures show grey (flat baseline, no meaningful band); bands come alive in autumn/winter when the same-week spread widens. Bands here are locally computed anomaly signals, not Japan's own fixed epidemic-onset (1.0/sentinel) or alert (30/sentinel) thresholds.
Neither a population rate (like the UK) nor a percent of visits (like the US) — so raw values aren't comparable across layers.
Source: JIHS Infectious Diseases Weekly Report (IDWR). Bands are computed by this site's extractor; see the JSON's band_config field for the exact thresholds.
The Australia layer shows ASPREN (Australian Sentinel Practices Research Network) surveillance: ~300 sentinel general practices across all 8 states and territories report weekly ILI notifications per 1,000 consultations. The report is published fortnightly, not weekly.
Every other layer on this map (England, Europe, US, Japan) bands each region by its own same-week history — a northern-hemisphere-friendly method where "high for this time of year" is intuitive. Australia is different for two reasons: the flu season is inverted (Jun–Sep), and ASPREN publishes its own government-endorsed activity thresholds: Baseline <9 / Normal 9–13 / High 13–16 / Epidemic >16 per 1,000 consultations. Those are the authoritative Australian interpretation, so this layer uses them to pick the band.
To keep the whole map readable at a glance, the shared 5-band colour scale is used everywhere: Very low / Low / Medium / High / Very high. ASPREN's local labels map onto the shared vocabulary as: No activity → Very low, Baseline → Very low, Normal → Low, High → Medium, Epidemic → High. Baseline maps to Very low (rather than a naive 1:1 to Low) because ASPREN's "Baseline" band explicitly includes zero — it means "below the elevated-activity threshold", not "moderately low". Epidemic caps at High (rather than Very high) because it's ASPREN's alarm threshold, not the theoretical maximum. The tooltip on each jurisdiction still shows the exact ASPREN threshold that put it in that band. The colour tells you how active; the tooltip and this About tell you which ruler.
The Australian Capital Territory is a tiny enclave inside NSW. ASPREN's own map does not draw ACT as a separately coloured polygon, so we fall it back to whatever band NSW is showing (tagged in the tooltip). ACT's separate reader count is reported by ASPREN but only appears in the line-chart figure, not the map.
Source: ASPREN Update (fortnightly PDF). Bands are read directly from ASPREN's Figure 3 activity map; see this site's data/australia-ili.json and band_config for the exact thresholds.
The Hong Kong layer shows the Centre for Health Protection (CHP) sentinel surveillance of private medical practitioner (PMP) clinics: general practices across Hong Kong report weekly influenza-like illness (ILI) cases per 1,000 consultations. It is clinician-diagnosed and syndromic, not lab-confirmed. Hong Kong is drawn as a single shape, with a dot so it stays visible when zoomed out; it is included as a well-reported indicator for the wider Pearl River Delta / southern China region.
The same way as Europe, the US and Japan: this week's rate is compared with the same week in previous seasons (up to 8), and the colour says how unusual it is for this time of year. Consultation patterns during and immediately after COVID-19 (2020–2022) were so distorted that including them drags the "normal" baseline into a range that isn't normal at all, so those years are excluded. Hong Kong has both a winter and a summer flu season, so "high for this week" is the meaningful comparison.
CHP also runs a second network in public Family Medicine Clinics (FMC). Its ILI rate has sat at roughly three times its pre-COVID level since 2023, a shift in who uses those clinics rather than in flu itself, which would keep it permanently at "Very high". The FMC rate is shown in the hover panel for context, alongside CHP's own one-line reading of both networks.
Source: CHP weekly ILI consultation rates. See this site's data/hongkong-ili.json and band_config for the exact thresholds.
The Korea Disease Control and Prevention Agency (KDCA) runs a national network of sentinel primary-care clinics that report weekly influenza-like illness (ILI) per 1,000 outpatients: clinician-diagnosed and syndromic, not lab-confirmed. This layer uses the national figure.
KDCA sets its own epidemic threshold each season (12.9 per 1,000 for 2026–27; 9.1 for 2025–26), calculated from recent seasons' non-epidemic levels. It is a single line: a week is either above it or below it. Rather than stretch that into our five-colour scale, Korea is drawn on its own terms: hatched when the latest week is above KDCA's epidemic threshold, and a plain outline when below. The hover chart shows the weekly rate against the threshold line, so you can see how far above or below it Korea sits.
Hatched means "above KDCA's epidemic threshold this week", not a level of severity comparable with the coloured layers. KDCA's formal epidemic advisory is issued and lifted separately (lifting needs several weeks in a row below the threshold), so this layer can briefly differ from the official advisory status. Province-level figures exist only from the 2026–27 season, so the layer stays national for now.
Source: KDCA infectious disease portal (weekly sentinel ILI) and KDCA's season-start announcements of the epidemic threshold. See this site's data/korea-ili.json.
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