A straight answer to the question everyone asks when they feel sick.
IsItFluSeasonYet.com pulls weekly CDC surveillance data and translates it into one clear answer — is flu actually active right now, in your region — plus the guidance most health sites never bother to give you: what to do about it today.
What this site is
It's a flu activity tracker built around a real answer. Not "flu season typically runs October through May" — that's a Wikipedia sentence. This site answers: is flu circulating right now, how bad is it, and what should you actually do about it?
The yes/no verdict at the top is driven by real CDC surveillance data for your HHS region. Below it, the page walks you through everything from whether to test today to how the current season compares historically — each section designed to answer a specific question a real person has when flu is going around.
Why we built it
The CDC publishes excellent flu surveillance data every week. Virtually no consumer-facing site surfaces it in a way that answers the question a normal person is actually asking. Medical sites explain what flu is. Pharma sites try to sell you something. Local news runs "flu activity high in [state]" headlines with no follow-through. None of them tell you whether you should test today, or whether a flu shot this week still makes sense, or how many weeks are likely left in the season.
We built the site we wished existed — one that treats CDC data as the foundation of a useful tool, not a citation at the bottom of a listicle.
What's on the page
At the top of the page you get YES, NO, or MAYBE in plain language, color-coded by severity, with a one-line qualifier that tells you what that means right now — not in general. A thin bar along the bottom of that section reflects your region's current activity level at a glance.
How Active Is Flu? immediately below the hero is the activity block — a 5-segment meter, a plain-language read on what the numbers actually mean, and the full season chart showing every week of the 2025–26 season so far. You can see at a glance whether flu is climbing, peaked, or winding down.
Section I — Should I Test Right Now? shows a testing recommendation calibrated to the current activity level and lab positivity data. At Moderate and above, antivirals like Tamiflu must be started within 48 hours of symptom onset — which means testing early, not waiting. To the right of the recommendation is a live respiratory activity widget showing what else is circulating: COVID, RSV, and pollen. If something other than flu is the dominant signal, the widget updates the recommendation context accordingly. Below that is a symptom triage table comparing flu, cold, and allergies side by side so you can make a more informed guess before you even get to a pharmacy.
Section II — Is It Too Late to Vaccinate? uses the historical peak week for your HHS region and the two-week window for a flu shot to reach full effectiveness to tell you whether vaccination still makes meaningful sense. A visual timing track shows where you are in the season arc relative to peak, so the answer isn't just words — it's a position. The recommendation updates week by week as the season progresses.
The season recap card summarizes the 2025–26 season with the peak severity, when it peaked, how many weeks it's been active, and the dominant strain — and links to a full recap page with the complete season chart, regional breakdown, and season narrative.
Section III — By Region only appears when regional variation is actually interesting — meaning at least one HHS region is at High or above, or your region differs meaningfully from the national picture. When it shows, it leads with a one-sentence summary and lets you expand to the full 10-region breakdown if you want it.
Section IV — Essentials is a compact list of products that are genuinely useful during flu season: rapid test kits, hand sanitizer, humidifiers, masks, and thermometers. Affiliate links — see the disclosure below.
The respiratory activity widget
The widget in Section I — "What's Going Around" — is a composite signal, not just flu data. It pulls from a dedicated respiratory activity service that combines CDC ILINet flu data, COVID wastewater surveillance, RSV surveillance, and regional pollen levels into a single ranked view. The idea is that if you have symptoms and flu activity is low but RSV is high, the most useful thing the site can do is tell you that clearly — not just confirm flu is quiet.
When pollen, RSV, or COVID outranks flu as the dominant circulating signal, a context note automatically appears below the widget to flag it. The dominant signal drives the testing recommendation language in the left column.
How the activity level is calculated
The core metric is weighted ILI% — the percentage of outpatient visits attributed to influenza-like illness, reported weekly through the CDC's ILINet surveillance network. ILINet collects data from thousands of sentinel providers across the country, making it the most reliable continuous measure of flu activity available in the US.
We map that percentage to a 0–5 scale calibrated against CDC historical thresholds. The CDC's national baseline is approximately 2.5% ILI; activity above that is considered elevated. Level 0 (None) is the off-season baseline. Level 2 (Low) means roughly 1 in 50 doctor visits are flu-related. Level 3 (Moderate) is widespread activity — about 1 in 25 outpatient visits. Level 4 (High) is peak-adjacent territory. Level 5 (Very High) means more than 1 in 8 visits, which by any measure is a heavy season.
The displayed level reflects your HHS region's activity when we know your location, or the national figure when we don't. National and regional data can diverge significantly — a severe season in the South may show Very High nationally while the Northeast is still at Low.
Data sources
Flu activity data comes from the Delphi CMU Epidata API, which mirrors CDC FluView ILINet data in near-real-time. The API is free, requires no key, and provides national and regional ILI% figures going back to 1997. Clinical lab data — strain typing and test positivity — comes from the same source via the FluView Clinical dataset.
The respiratory activity widget draws on additional data streams: COVID activity via wastewater surveillance, RSV via CDC surveillance data, and pollen via a regional pollen API — all aggregated and cached by a dedicated Cloudflare Worker that updates throughout the day.
Location is resolved via your browser's Geolocation API and reverse-geocoded through OpenStreetMap Nominatim. Coordinates are used only to determine your HHS region and are never stored or transmitted beyond what's needed to fetch your regional data.
Data updates weekly, typically on Thursday, when the CDC publishes the prior week's surveillance report. The dateline below the site header shows the exact reporting week so you always know how fresh the numbers are.
HHS regions — why flu data is regional, not local
The CDC tracks flu at the national level and across 10 Health and Human Services (HHS) regions. Unlike pollen, which varies meaningfully block-by-block, flu spreads at a regional scale — a strain moving through the Southeast affects all of Alabama and Georgia in roughly the same wave. City-level flu data simply doesn't exist in the surveillance network.
When you enter a location, the site maps your state to its HHS region and uses that region's ILI% for your activity level, vaccine timing calculation, and test recommendation. The season chart and historical comparisons use national figures, which are available for the full season arc going back to week 40 of each flu year.
The weekly data lag
CDC FluView data always reflects the prior week — there's roughly a 7-day lag between real-world conditions and reported numbers. This is a property of the surveillance system itself, not a limitation of this site. The dateline in the header makes the data vintage explicit so there's no ambiguity about what "current" means.
Clinical lab positivity — the share of tests coming back positive — updates on the same weekly cadence and appears in Section I as an early-warning signal. Positivity often rises ahead of the ILI numbers, so it's useful context when the headline activity level feels low but something is starting to move.
The guides
Beyond the tracker, the site has ten in-depth guides covering the questions that come up most during flu season: how long flu lasts, when to get a flu shot, whether it's worth it, antivirals and Tamiflu, what to do at home when you're sick, flu in kids, high-risk groups, how the flu shot differs from year to year, and how to tell flu from a cold or from allergies. They're at isitfluseasonyet.com/guides.
Who built this
This site is part of a small network of seasonal condition trackers built to answer the questions people actually type when they're trying to figure out what's happening — with their health, outside, or both. The allergy counterpart lives at isitallergyseasonyet.com. The mosquito tracker is at isitmosquitoseasonyet.com.
Editorial decisions — what to show, how to frame it, what thresholds to use, what the triage table says — are made here, not by committee. If a threshold seems wrong for your region or you have a question about how something works, the contact page goes directly to the person who built it.
Nothing on this site is medical advice. For anything beyond general guidance, talk to your doctor. See our Terms for the full disclaimer.
Affiliate disclosure
Some product links — test kits, thermometers, humidifiers, masks, and hand sanitizer in the Essentials section and throughout the guides — are Amazon affiliate links. If you purchase through one of these links, we may earn a small commission at no additional cost to you. Products are chosen because they're genuinely useful during flu season, not because of commission rates.
Get in touch
Questions, data corrections, or feedback: [email protected], or use the contact form.