Guides

Practical writing on flu — when to test, whether antivirals are worth it, how to read the season, and what to actually do when you're sick. Grounded in CDC surveillance data and published clinical sources.

When you're sick right now

• Is it flu, a cold, or COVID?
  The symptoms overlap enough to be genuinely confusing — fever, body aches, fatigue, cough. Here's how to tell them apart, why the current regional activity level matters for your odds, and when to test for which.
• Allergies vs. flu: how to tell the difference
  In spring, pollen season and flu season overlap. Sneezing, congestion, and fatigue can point to either one — but flu has a 48-hour antiviral window that allergies don't. Here's how to tell them apart fast.
• Antivirals: the 48-hour window and whether they're worth it
  Tamiflu, Xofluza, and Rapivab all work on the same basic principle — they're only effective if you start them within 48 hours of symptom onset. What the evidence actually says about benefit, who qualifies, and why the clock starts when you feel it, not when you test.
• How long does the flu last?
  Day-by-day progression, what's normal versus a warning sign, when to return to work or school, and the post-flu fatigue that catches people off guard.
• Flu at home: what to actually do
  Fever management, hydration, what OTC medications do what, and the specific signs that mean it's time to go to urgent care or the ER.

Prevention and vaccination

• When to get your flu shot — and whether it's too late
  The CDC says "by the end of October," but the real answer depends on where you are in the season. This guide explains the two-week activation window, how regional peak timing varies, and how to use the vaccine window tool on this site to get a real answer for your location right now.
• Is the flu shot worth it?
  An honest look at the evidence — what the vaccine does and doesn't do in a given year, why effectiveness varies, who benefits most, and what the critics get right and wrong.
• High-risk groups: who needs to be most careful
  Adults 65+, young children, pregnant women, and people with certain chronic conditions face meaningfully higher risk from flu complications. What that risk looks like and what to do differently.

Understanding the season

• When does flu season start and end?
  The US flu season runs roughly October through April — but that average hides enormous variation. Some seasons peak in December, others in February. Here's what drives early versus late seasons, how the CDC tracks it week by week, and what to watch for in your region.
• Flu in kids: what parents need to know
  Children under 5 — especially under 2 — are at elevated risk for serious flu complications. Symptom differences, when to call the pediatrician, and why antivirals are often recommended earlier in kids than in adults.

Flu activity by region

Live activity data and regional deep-dives for each of the 10 HHS regions — peak timing, what drives the season locally, and recent season history.

• HHS Region 4 — Southeast AL FL GA KY MS NC SC TN
  The Southeast leads the nation — flu arrives here first almost every year, often peaking in November or December while the rest of the country is still at Very Low.
• HHS Region 6 — South Central AR LA NM OK TX
  Texas's scale dominates the region. When Houston and Dallas hit High, the national ILI number moves. Live activity data for HHS Region 6 updated weekly.
• HHS Region 2 — New York & New Jersey NJ NY
  The densest transit corridor in North America makes flu move fast. When Region 2 peaks early, the national peak usually follows within a month.
• HHS Region 3 — Mid-Atlantic DC DE MD PA VA WV
  From the Amtrak corridor connecting DC, Baltimore, and Philadelphia to rural West Virginia — the most demographically varied region in the country.
• HHS Region 5 — Midwest IL IN MI MN OH WI
  Long, cold winters mean sustained peaks. The Midwest doesn't get the most dramatic spikes, but the elevated activity can hold for six or seven consecutive weeks.
• HHS Region 1 — New England CT MA ME NH RI VT
  Boston's college population and dense transit drive an early-January peak, while Maine, New Hampshire, and Vermont often lag by one to two weeks.
• HHS Region 7 — Plains IA KS MO NE
  Kansas City is the bellwether for the region. Cold, dry winters and significant rural healthcare gaps make flu hit harder than the ILI numbers suggest.
• HHS Region 8 — Mountain CO MT ND SD UT WY
  Ski season concentrates visitors from high-activity regions in gondolas and lodges from Thanksgiving through March — a unique early-season spread dynamic.
• HHS Region 9 — Pacific Southwest AZ CA HI NV
  The West Coast lag is real — Region 9 typically peaks in February, 4–6 weeks after the Southeast. Hawaii is a year-round outlier with no sharp seasonal spike.
• HHS Region 10 — Pacific Northwest AK ID OR WA
  Rainy winters keep people inside from October through April. Alaska's isolated rural communities face some of the highest flu hospitalization rates in the country.

Season history

How bad was each flu season? Live Delphi CMU data for each year — peak severity, dominant strain, regional breakdown, and week-by-week arc back to 2019.

• The worst flu seasons since 2000 — ranked
  Every flu season since 2000 ranked by peak ILI% severity, with peak month, active weeks, and context on the years that stood out. Live data from CDC FluView.
• Season comparison chart Interactive
  All recent seasons on the same week-by-week timeline — see at a glance whether this year is running ahead of or behind the worst years in recent memory.
• Season archive: 2019–present Overview
  Individual deep-dives per season — severity, arc chart, strain breakdown, and regional data. One page per year, data live from CDC FluView.
• 2024–25 flu season
  The current season — full arc as it happened, peak severity, strain breakdown, and how each of the 10 HHS regions fared.
• 2023–24 flu season
  A moderate season with an unusually early December peak. H1N1 dominated but with notable H3N2 co-circulation in the Southeast.
• 2022–23 flu season
  One of the worst in a decade — an early, severe H3N2 season that peaked before Christmas and overwhelmed pediatric hospitals in several regions.
• 2021–22 flu season
  Flu returned after a near-absent 2020-21 season, with a modest mid-winter peak as immunity gaps from the prior year began to close.
• 2020–21 flu season COVID year
  Masks, distancing, and reduced travel nearly eliminated flu — the lowest recorded season in modern surveillance history. Not a reliable baseline for comparison.
• 2019–20 flu season
  A high-severity H1N1 season cut short by COVID-19 in March 2020 — the last "normal" season before the pandemic disrupted flu surveillance for three years.