Outbreak Outlook - National - Mar 31

The end of flu season is in sight

Respiratory Diseases

Influenza-like illness

Outpatient influenza-like illness (ILI) has dipped to 3.3%, edging closer to the 3% threshold that marks the end of flu season. I expect we’ll get there next week or the week after.

One thing to watch: an increasing proportion (now 6.4%) of specimens are influenza B. This pattern is typical for this time of year, but it does sometimes cause a late-season rise in outpatient ILI activity. Flu B is typically thought of milder compared to flu A, but having recently recovered myself, I have doubts!

All ages are seeing continuing declines in activity. Children ages 0 to 4 have finally dropped below the 10% mark for outpatient ILI, now at 9.3%. School-age children are seeing improvements as well, now at 5.4%. The older age groups are all below 3% and improving.

Most of the country is now registering low or minimal levels of flu activity—with a few exceptions. The Northeastern region is still experiencing high levels of outpatient activity in some places, as are Louisiana and Oregon. However, the Northeast’s emergency department visits for influenza are low and falling (see below).

I expect we will see improvements in the weeks ahead in the remaining hotspots. But for now, continued caution is warranted.

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COVID-19

Covid-19 is stable. Wastewater activity is moderate in the South but has fallen to low levels in the other regions. Trends are pretty steady at this point, with no major increases or decreases evident in any region.

I do suspect that given the relatively quiet Covid-19 winter season, we are in for a significant summer wave. The timing is highly uncertain, but in previous years, June has been the earliest start. I'll keep an eye on things and let you know when activity begins to rise.

Trips to the emergency department continue to decline very slowly, down to 0.6% of all ED visits last week. Hospitalizations have declined to a low 2.3 hospitalizations per 100,000 people.

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RSV & Other Bugs

RSV activity is low and declining, which is typical this time of year. We are in the off-season.

However, a bunch of those pesky bugs that cause cold- and flu-like symptoms are spreading widely or picking up steam right now.

• Adenovirus has been increasing since February, though it is still below the peak it reached in December.

• Human coronaviruses are still quite high, but are slowly decreasing.

• Human metapneumovirus continues to climb and is likely getting close to its peak for the year.

• Parainfluenza and rhinovirus/enterovirus remains fairly low, but are on an increasing trend.

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Norovirus

Norovirus persists at very high levels, but is declining ever so slowly. Rates have decreased each week for the past week, landing at 17.5% test positivity this past week. Rates are highest in the Midwest and lowest in the Northeast.

Norovirus tends to persist well into the spring, so while relief is getting closer, it is likely that we still have several more weeks of elevated rates ahead of us.

Source: CDC

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Food recalls

The following foods are being recalled because they are contaminated. Please check your cupboards and throw out any of these items:

New:

• Nothing new this week

Previously reported:

• Enoki mushrooms sold under Daily Veggies brand (more info)

• Hot pot sauce sold under Wangshihe brand (more info)

• Prepared vegetables sold at Tokyo Central/Marukai stores in California (more info)

• Wild Coast Raw Chicken Formula [for cats] due to potential contamination with avian influenza H5N1 (more info). This poses a risk to cats who ingest the product, as well as to humans handling the product.

• Lyons ReadyCare and Sysco Imperial Frozen Supplemental Shakes in various flavors (more info)

• Canned Tuna sold under Genova, Van Camp’s, H-E-B, and Trader Joe’s brand names (more info)

• If you have food allergies, you may wish to review these FDA safety alerts and USDA alerts for foods with undeclared allergens.

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In other news

• I am moving to my summer publication schedule this week, so this is the last free national edition of the season.

  • Paid subscribers will continue to receive the national edition throughout the spring and summer months. As a reminder, I am also offering twice-weekly measles updates to paid subscribers.

  • The winter publication schedule, including a free national version, will resume in October.

• As of March 28, measles cases in Texas and New Mexico rose 20% from the previous report, with Texas reporting 400 cases—270 in Gaines County—and two deaths (one still under investigation). New Mexico's total is now 44. Two additional states are also seeing outbreaks of 10 or more cases. The CDC reports 483 cases nationwide for 2025 to date, surpassing all of 2024's total.

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Photo by Jake Weirick on Unsplash