Respiratory Diseases

Influenza-like illness

Flu activity continued to decline this week, but there’s a caveat: school-age children are seeing a rebound in activity. Although the increase is small, kids are often the first to register new flu trends, so I’m watching closely. Either this is a brief bump that will pass quickly, or it’s the beginning of a larger spike. We’ll know more in the next week.

Nationally, emergency department visits for flu fell from 4.2% to 3.2%, and outpatient influenza-like illness (ILI) also declined from 5.3% to 4.4%. (As a reminder, outpatient ILI is the percentage of visits to the doctor that are for fever and cough or sore throat.) These levels are still quite high, but a huge improvement from the holiday season peak of over 8% for outpatient ILI.

Children ages 0-4 continue to see improvements, with outpatient ILI falling from a recent high of 19.9% to 12.4%. This current level is similar to what we saw in mid-December, so still quite high but heading in the right direction.

The 5-24 age group held mostly steady at the national level at around 7.4% outpatient ILI. However, the national number conceals more prominent rebounds at the state and local level, and this reversal is visible in emergency department data as well. Those signals are what have me cautious for activity in the next week or two.

Adult age groups are all dropping steadily, though again they are often later to see new trends.

This time of year is when I begin to look for a gradual shift from influenza A predominance to influenza B. Right now, flu A still constitutes 94% of specimens tested. The vast majority of those are H3N2 subclade K, which is the new variant that emerged this year. Flu B is still a minority (5.7%) of specimens. Thankfully, the flu shot covers both.

COVID-19

Covid-19 activity is improving nationally, hopefully rounding out what was a fairly tame season. However, the small rebound I see among school-age kids in influenza data is also visible in the Covid-19 data. That’s another thing I will be watching in the weeks ahead.

Emergency department visits fell from 1.0% to 0.8%, at the national level, and wastewater levels declined in most of the country. The Midwest remains the most affected region, with several states still at very high wastewater levels and ED visits running higher than elsewhere. A couple of states saw wastewater jump unexpectedly this week, but the overall trend is encouraging. The West remains particularly quiet, with very low wastewater activity throughout.

RSV

RSV activity held steady nationally this week, with ED visits flat at 0.4%. However, there’s a patchwork of activity across regions.

The South has the highest activity, with Delaware and Arkansas both above 1% of ED visits. The Northeast is seeing a slight uptick, with New Jersey and Rhode Island leading the region. The Midwest ticked up modestly, led by Iowa. The West remains quiet overall, with Hawaii improving after a spike last week.

Norovirus

Norovirus activity is holding mostly steady at around 10-15% test positivity, well below last year’s peak of nearly 25%. All four regions of the country are in decent shape.

Food recalls

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

New:

• Suzanna’s Kitchen Recalls Ready-To-Eat Grilled Chicken Breast Fillet (more info)

Previously Reported:

• Super Greens supplement powder (more info)
• Spring & Mulberry chocolate bars (more info)
• Pecorino cheese from various brands, including Boar’s Head and Members Mark (more info)
• Sea Moss Gel Superfood (more info)
• Klong Kone Shrimp Paste, sold exclusively at Golden Land in Des Moines, Iowa and Terri Lee Oriental Groceries in Maywood, New Jersey (more info)
• Primavera Nuevo tamales, various flavors (more info)
• There is a big recall of hundreds of products — from Airhead candies to meat to Splenda packets — that passed through a single distributor and were sold to over 50 stores, primarily in Minnesota and Indiana. I strongly urge you to check out the list of stores (here) and if you’ve shopped at one of them recently, check out the much longer list of items that are being recalled (here)

In other news

• New outbreak resource. I’m launching a new resource called FOI Clinical, designed for clinicians who want to stay informed about outbreaks and infectious disease activity without digging through surveillance reports. Where Force of Infection covers seasonal respiratory viruses for a general audience, FOI Clinical focuses on reportable diseases like measles and pertussis, emerging outbreaks, and infectious disease-specific policy changes (e.g., ACIP proceedings) that could affect patient care. The first edition is expected next month, and founding members can lock in early pricing. Learn more or sign up at foiclinical.com.

FOI Clinical: A new outbreak monitoring service

Yesterday, the U.S. CDC issued a Health Alert Network (HAN) advisory about New World screwworm cases on the Mexico side of the Texas-Mexico border. New World screwworm is primarily a disease of livestock, though humans can become infected. There are currently no human or animal cases in the United States, though it is an encroaching threat.

Force of InfectionCaitlin Rivers

• U.S. leaves WHO. The United States has completed its withdrawal from the World Health Organization, one year after President Trump announced the plan to leave. The administration cited WHO’s mishandling of the pandemic, including delays in declaring a global health emergency and failing to adopt meaningful reforms. The U.S. still owes about $280 million in unpaid dues, and the U.S. hasn’t finished working out issues like lost access to early warning data from other countries.
• Measles outbreaks continue. South Carolina’s measles outbreak has grown to 700 cases, with 54 new infections confirmed in three days. The US has reported 416 cases already this month, more than we see during most entire years. The outbreak on the Utah/Arizona border is also growing. The United States will likely lose its measles elimination status, which it gained in 2000, when the Pan American Health Organization meets in April. Last year saw 2,255 cases and three deaths, the most since 1991. CDC principal deputy director Ralph Abraham called the potential loss of elimination status the “cost of doing business” and framed vaccination as a matter of “personal freedom.” I spoke to PBS NewsHour last night about the measles situation and our withdrawal from WHO.
• Winter storm threat. I’m trying to get regional editions out later today in case we lose power tomorrow due to the big snow/ice storm, but we’ll see! Thanks for your patience, stay safe and warm.

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