Outbreak Outlook - National - December 4

Influenza-like illness, Covid-19 and RSV all up as we head into the holidays

Respiratory diseases

Welcome back to Outbreak Outlook! This update kept growing and growing as I found more information that I wanted to share, so I hope you’re in the mood for a deep dive. If not, suffice it to say that all of the big three (flu, Covid-19 and RSV) are increasing around the country.

Influenza-like illness

Unsurprisingly, influenza like illness activity is still increasing. During the week ending November 25, around 3.9% a visits to the doctor were for fever and cough or sore throat, up from 3.7% the week before. This level of activity is quite a bit higher than what we normally see this time of year.

By region: The South remains most impacted, with “very high” levels of activity in Louisiana and South Carolina. The rest of the Southern region is reporting high or moderate ILI levels. Parts of the West, including California, are also in the “high” category, along with New York City and Puerto Rico. Only the Midwest and Northeast have avoided significant flu impacts so far this season.

By age: As usual, young children are remain most affected by ILI activity—11% of visits to the doctor were for ILI in children ages 0-4, compared to 6% in people ages 5 to 24. Older group remain below 3% (show in plot below). However, hospitalization rates are actually highest among older adults.

Remember that there are treatment options available for influenza that can prevent progression to severe illness. Keep that in mind as we had into peak flu season in the weeks and months ahead.

---

Covid-19

Covid-19 activity is creeping up as we head into the winter months. The week ending November 25 saw over 19,000 new hospital admissions for Covid-19, which puts us on par with the peak of the summer wave. While concerning, we remain far below the heights of last winter's Omicron surge, when weekly hospitalizations exceeded 150,000.

Nonetheless, Covid metrics are definitively rising - emergency department visits and test positivity have picked up along with hospitalizations, and wastewater concentration is rising as well. So my current thinking is that this reflects a real winter uptick, rather than a minor fluctuation.

By region: The number of new hospitalizations rose in all four regions of the country. Wastewater is increasing too. The Midwestern region is most affected, with both wastewater and hospitalizations clearly rising.

By age: I took a look at the latest hospitalization rates by age. Older adults are still most affected by severe Covid-19—hospitalization rates are highest by far among people over the age of 70. Right now, this age group is seeing a significant uptick.

By severity: Weekly hospitalization rates for Covid-19 are far above those for influenza right now, and the proportion of overall deaths attributed to Covid-19 is also much higher. (Both viruses can be dangerous, to be clear.) However, far more people have received their annual shot for flu (39%) compared to Covid-19 (16%).

---

RSV

RSV activity is still up, up, up. PCR test positivity is currently in the 15% range, which is close to the 20% or so that we often see during peak season. Activity has been rising since early September, so we are already three months into the season. I expect RSV activity to peak in the coming weeks, and decline as we head into the new year.

By severity: In terms of severe illness, hospitalization rates remain below last year's level so far. However, I took a closer look at the state level and found that states that experienced an earlier onset of their RSV wave, like Georgia and Tennessee, have hospitalization rates similar to last year. This suggests that by the end of the season, we may find the total burden of severe RSV illness this year reaches a comparable level to what we saw before. But this is somewhat speculation, so we'll see when the data comes in.

By age: Infants and young children have—by far—the highest rates of hospitalization for RSV. The good news is that we now have RSV shots available to help protect infants, both shots given directly to babies as well as vaccinations for pregnant women to confer antibodies to their babies. However, widespread access to these new RSV shots has been limited by shortages and various logistical troubles.

By race and ethnicity: I found some new (to me) data on hospitalization rates due to RSV, stratified by race and ethnicity. In early November, people whose race was reported as Black or Hispanic had the highest rates of severe RSV. Additionally, American Indian/Alaska Native populations also have consistently high rates of severe RSV.

---

Others

I’m monitoring several other respiratory viruses. 

• Human metapneumovirus, parainfluenza, and adenovirus are holding steady at low levels nationally. 

• Seasonal coronavirus levels also remain fairly low, but they have been drifting up in some parts of the country. Seasonal coronaviruses are a cause of the common cold.

---

Norovirus

Norovirus activity is surging as we move into the winter months. Nationwide, test positivity is over 10%, up from 6% at the beginning of November. This virus commonly rises through the winter months and peaks in late winter or early spring, so I expect activity to continue picking up in the months ahead. To prevent norovirus, wash your hands with soap and water. To avoid spreading the virus to others, stay home if you have any gastrointestinal symptoms.

---

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:

• The cut cantaloupe recall I have been reporting on for several weeks has expanded considerably. I recommend skipping the pre-cut cantaloupe altogether for a while — including both fresh fruit and fruit cups (more info)

• Peaches, nectarines, and plums sold in bags branded as HMC Farms and Signature farms (more info)

Previously reported:

• Multiple brands of pet food - dog, cat, and catfish food (more info here and here) (Note: this poses a risk to pets andto the people that care for them, since Salmonella can be acquired via handling of the contaminated pet food and/or contact with infected animals. Several human cases, including in infants, have been tied to the pet food.)

• Tyson chicken nuggets (more info) 

• Multiple brands of Apple Cinnamon Fruit Puree (more info)

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

---

In Other News

• Good news from www.covid.gov/tests: “Every home in the U.S. is eligible to order an additional 4 free at-⁠home tests beginning November 20. If you did not order tests this fall, you may place two orders for a total of 8 tests.” In related news, starting in early December, school districts will be able to order at-home tests for distribution in schools.

• While you’re at it, make sure your medicine cabinet is stocked for flu season. I recommend keeping some ibuprofen and acetominophen for everyone in your family, including children’s versions if needed. Also keep some rehydration fluids and masks on hand. These items can be hard to find during the height of flu season, so buy them now. For more recommendations on caring for someone who is ill, see my post from last fall.

• During the holiday weekend, there was an increase in reports about pneumonia cases in children in China, initially highlighted by ProMED, a disease reporting site. Some of the language used was similar to the earliest reports of what became Covid-19, including the words "undiagnosed pneumonia." This led to speculation that a new infectious disease threat was emerging.

  • For what it’s worth, I’m not worried yet. For one thing, the word “undiagnosed” only appeared in the title, not in the body of the report. There are no other indications that health authorities are struggling to diagnose these pneumonia cases.

  • Moreover, China only lifted its zero-COVID policy last winter. This is the first respiratory virus season with lighter infection control measures in place. I think it is likely that we are seeing China's version of the "tripledemic" - a spike in various common respiratory pathogens.

  • This explanation is supported by a recent dispatch from WHO identifying the rise in pneumonia to a potpourri of common pathogens.

  • But as always, outbreaks change constantly and so do what we know about them, so I will monitor to see how things develop.

Photo by Anne Nygård on Unsplash