Outbreak Outlook - National - March 18

Norovirus remains high, ILI and Covid-19 improving.

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Respiratory Diseases

ILI

Influenza-like illness (ILI) dropped again this week (thankfully!) to 3.75%, down from 4.1% the week prior. The national baseline is 2.9%, so we still have at least a few weeks yet to go, but at least trends are headed in the right direction. 

Status of flu B: This time of year we often see an uptick in influenza B, which is known for occurring later in the flu season and often impacts children and young adults more frequently. However, I don’t see much evidence that flu B is increasing in the data right now, it’s holding steady at about 33% of flu cases.

One cool fact: One lineage of influenza B, Yamagata, is thought to have gone extinct during the pandemic. The measures implemented to reduce SARS-CoV-2 transmission also greatly depressed influenza circulation, to the point that Yamagata appears to have been completely stamped out.

Trends by age: All age groups saw decreases in ILI activity, even the beleaguered 0-4 category. They finally dipped below 10%, to 9.8%.

Trends by region: All four regions of the country are seeing declining ILI activity. The Western region has lowest activity overall, heading toward 3% of outpatient visits for fever and cough or sore throat. The South and Northeast are nearly tied for second place. Even the Midwest, which struggled to turn the corner after an odd second peak in activity, is seeing improvements.

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COVID-19

Covid-19 activity continues to recede across the United States, with new weekly hospitalizations dipping to 4 per 100,000. This is substantially lower than where we were this time last year. I think we can reasonably expect continued improvements, perhaps even through summer if we are lucky. Wastewater concentration is also fairly low and dropping, which is further evidence that we are heading in the right direction.

All four regions of the country are seeing improvements in Covid-19 hospitalizations. The Western region is again in the best shape, with hospitalizations nearing 3 per 100,000. The Northeast and Midwest are a little further behind, in the 3.5-4 range. The South struggled to turn the corner coming out of the winter season, but they too are seeing declining levels of Covid-19 hospitalization and wastewater concentration.

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Other Bugs

• Seasonal coronavirus activity remains very high but may be coming down. This is likely peak season for this set of viruses, which cause cold-like symptoms. Distinguishing cold symptoms from allergy symptoms is tough this time of year. Itchy eyes are more common with allergies, whereas a sore throat is more common for a cold.

• Metapneumovirus activity may be ticking up. Symptoms range from mild cold-like symptoms, including cough, fever, and nasal congestion, to severe respiratory distress such as bronchiolitis and pneumonia in more vulnerable populations. If you get a bad infection this time of year, metapneumovirus and influenza B both come to mind as possibilities.

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Stomach Bugs

Norovirus activity remains high and is rising for most of the country, with test positivity into the double digits. If you’ve been following along with my previous reports, you’ll know that this time of year is peak norovirus season. Activity will likely remain high through April.

The best way to prevent norovirus is to wash your hands using soap and water. Prevent onward transmission by staying home until 48 hours after symptoms resolve, and avoid preparing food for others during that time.

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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

• None

Previously reported:

• Multiple brands of cinnamon sold at discount stores, for lead contamination. The best resource I found to quickly survey affected products is here.

• Raw Farm brand cheddar cheese (more info)

• Sargento Foods shredded cheese. This recall affects food service customers and does not include Sargento-branded retail products. (more info)

• A big recall of Queso Fresco and Cotija Cheese is affecting numerous consumer products: (more info)

• Robitussin Honey CF Max cough syrup products (more info)

• 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

• Chicago's measles outbreak continues to grow, with ten cases now linked to individuals residing in a local migrant shelter. Reports indicate that the shelter is overcrowded by hundreds of residents, and there is a substantial population of infants who are currently too young to receive vaccinations. In response to this situation, local health authorities implemented a mass vaccination campaign, administering the MMR vaccine to hundreds of shelter residents.

• Liberia held a remembrance service this week in honor of the more than 11,000 people who died during the 2014-2015 Ebola epidemic in West Africa. The epidemic is the largest Ebola outbreak in recorded history, tallying over 28,000 recorded cases across Liberia, Guinea and Sierra Leone.

Photo by Ekaterina Novitskaya on Unsplash