Outbreak Outlook - National - January 8

It is still peak season 📈

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This week I am reporting on data from the week ending December 30, which is squished between two major holidays. Data and assessments should be considered provisional.

Respiratory diseases

Influenza-like illness

Nationwide, influenza-like illness (ILI) activity continues to accelerate as we head deeper into winter. ILI metrics went up again — 6.8% of visits to the doctor were for fever and cough or sore throat during the week ending December 30. That's close to the highest levels seen during the 2021-2022 flu season. In that season, flu activity hit multiple peaks over several weeks, topping out around 7-8% at the worst points. I don’t know what this season’s peak will be, but I expect it to hit this month.

By region: The South and West regions stand out as most intense, with states like South Carolina, Tennessee, Wyoming and New Mexico already exceeding 10% ILI, beyond peak levels from last winter. More regions are now following concerning trajectories. The Midwest and Northeast saw sizable rises this past week as well, with most states in the 4-6% range. (The Northeast is being skewed by very high levels of activity in New Jersey, but most other states in the region are doing ok.)

By age: The littlest ones are still having a tough time. ILI activity in kids age 0-4 rose again this week to 15%, up from 14% the week prior. On the bright side, activity in people ages 5-24 actually fell slightly to 10%, though this may be a holiday-related blip and not a true decrease. Continued increases were seen in older age groups, with the 25-49 age group rising to nearly 7%. Older adult age groups were below 5%.

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Covid-19

I have received lots of questions and concerns about the JN.1 variant. First, I'll tell you what we know, and then I'll tell you what I make of it.

First, the variant recently became dominant in the United States, after ascending to dominance in various other countries around the world. The variant has an unusual number of mutations, raising concern about its potential to fuel a new surge. 

Covid-19 hospitalizations are still rising nationwide, with over 29,000 new admissions last week - an increase over 25,000 from the prior week. The most intense activity remains centered in the Midwest and Northeast.

Multiple states across those regions now exceed 10 or even 13 new admissions per 100,000 residents. The South and West are trending upwards as well, with states like Arizona, Nevada and Oregon showing significant jumps this past week.  

Also, wastewater concentration is high and increasing across the U.S., especially in the Midwest. We no longer have reliable data on the number of cases (vs hospitalizations), so wastewater is our only real measure of how much virus is circulating.

However, I don’t like to consider wastewater concentration as a quantitative metric. It’s not clear to me that its relationship to infections is stable over time, or comparable between regions. Instead, I rely on it as a qualitative indicator. This is where I may depart from some of my epidemiology colleagues—I’d say the science is not quite settled about how best to incorporate wastewater.

Wastewater concentration by region. Source: CDC

So what does this all mean? There is certainly reason for caution this month, given all the viruses that are going around, including Covid-19. However, I am still not expecting an Omicron-level wave based on what I’m currently seeing, but that opinion is weakly held, meaning I am prepared to change my mind every time new data come in.

Overall, I expect the weeks ahead to bring continued elevated Covid-19 activity, similar to last winter's seasonal wave. The peak will likely occur this month, though the timing remains unclear. I will keep closely tracking the trajectories through January in terms of cases, hospital burden and other key metrics.

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RSV

Hmm, the data on RSV activity is pretty hard to interpret this week. It’s jumping around. I can say with confidence that the South is improving markedly (which is why the plot below looks pretty good, but this is mainly driven by the South), but activity everywhere else remains high. Whether RSV season has peaked in the other three regions is hard to tease out. We’ll have to wait until next week, when holiday disruptions have eased, to see where things stand.

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Stomach Bugs (Norovirus)

Norovirus activity is increasing across the country, with test positivity in the double digits in every region. I expect activity to continue to increase through winter and into early spring. Norovirus, which causes vomiting and diarrhea, spreads easily between people. To prevent infection, wash your hands well with soap and water. If you do get infected, be aware that you can remain infectious even after symptoms subside. The CDC recommends that you stay home and avoid preparing food for others for two days after recovery.

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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 this week:

• Charcuterie meats sold by Fratelli Beretta (more info)

• Ground beef sold by Valley Meats and Scanga Meat (more info, more info)

Previously reported:

• Pet food sold by Blue Ridge Beef (more info). Pet food can pose a risk to humans through cross contamination.

• Tons of different granola and oatmeal products from Quaker (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

• In Alaska, a polar bear's death from highly pathogenic avian influenza marks a global first, indicating the virus's persistence in wild populations. The bear likely ingested the virus while scavenging dead birds. This incident highlights the extensive impact of H5N1, which has affected various wild birds and mammals worldwide. H5N1 has been very persistent, maintaining itself in wild populations far from domestic flocks.

• In the Houston area, students are grappling with grief and mental health challenges following the deaths of parents and caregivers from Covid-19. With federal stimulus funding for schools ending and the Texas state legislature providing no additional funds for public schools in the 2023 session, school districts face tough decisions about maintaining mental health support. The sudden loss of a parent significantly impacts students' academic performance and overall well-being.

Photo by Raimond Klavins on Unsplash