Summary: Week of 8/12/24

We continue to monitor the evolving H5N1 influenza virus situation. As we do, a quick reminder that Biobot’s influenza A assay detects the H5N1 influenza subtype, which is an influenza A virus, but does not distinguish between the different subtypes of influenza A (e.g. H5N1 vs H1N1). 

Thankfully, we still have not seen large, widespread increases in influenza A concentrations. Data through week 32 (August 10) also indicate that influenza activity remains low in the four US regions. We want to highlight some important points about the role of Biobot’s wastewater data in understanding the current circulation/risk of H5N1: 

• At this point, we cannot determine if any upticks we’ve observed are due to seasonal influenza A virus or if H5N1 could have played a role. 
• Biobot is currently testing for influenza A in 9 out of the 13 states with positive dairy herds (Texas, New Mexico, Kansas, Idaho, Ohio, North Carolina, Iowa, Wyoming, and Oklahoma), among several other states across the country. 
• Our current assays do not distinguish between human infections and infected animals shed into the wastewater system. 

This situation is rapidly evolving, and our team will continue closely monitoring H5N1. We will provide any additional information as it becomes relevant or available via Twitter and in the risk reports.

Biobot’s national wastewater network showed very low national concentrations of influenza A & B and RSV during week 32, while SARS-CoV-2 concentrations continued to increase. We are seeing early warning signs that the RSV season is approaching, with concentrations in the Midwest beginning to increase for the first time in months. Nationally, major clinical metrics remained low for influenza and RSV in week 31, while metrics for COVID-19 remained elevated. 

The Bottom Line: COVID-19 activity remains elevated and continues to increase across most of the country. Our recommendations to stay healthy are the same as in the winter: if you feel unwell, minimize contact with others, consider wearing a mask in crowded areas, and stay current with vaccinations and boosters.

National Outlook

RSV

Nationally, RSV concentrations remained very low in week 32. 

Influenza

Nationally, influenza A and B concentrations remained very low in week 32.  

Clinical data showed that the illness burden due to influenza remained relatively low in week 31. The percentage of outpatient visits for influenza-like illness (ILI) – typical in flu, RSV, and COVID-19 patients – held steady and remains below the national baseline of 2.9%, currently at 1.5%. FluSurv-NET reports that the influenza hospitalization rate per 100,000 persons also remains very low, currently at 0 in week 31. These metrics remain at levels we would typically expect for this time of year and indicate low influenza activity.

COVID-19

Wastewater data show that COVID-19 activity and community viral load increased during week 32. The national average SARS-CoV-2 wastewater concentration is now 728 copies per mL. 

Clinical COVID-19 metrics remain elevated. Test positivity continued to increase in week 31, currently at 17.6%, while COVID-NET reports that the national COVID-19 hospitalization rate is 2.9 per 100,000 persons. Deaths due to COVID-19 held steady in week 31 and currently represent 1.5% of all deaths in the US.

Regional

The South

RSV: In the South, RSV wastewater concentrations remained stable and very low during week 32.  

Influenza: Influenza A and B concentrations held steady at very low levels in the South during week 32. Clinical data continues to confirm that the disease burden due to influenza remains low—all Southern states remained in the minimal ILI activity level through week 31.  

COVID-19: SARS-CoV-2 wastewater concentrations held steady in the South during week 32, at 682 copies per mL. Georgia and Tennessee are the two Southern states in COVID-NET. Hospitalization rates remain elevated in both states, increasing in Tennessee in week 31. Rates might be decreasing in Georgia, however, other recent decreases have been corrected to increases, so it is unclear what the actual trend in the state is.

The Midwest

RSV: We saw the first signs that the RSV season is approaching, as concentrations slightly increased in the Midwest during week 32 for the first time in months. However, concentrations remain pretty low.  

Influenza: Influenza A and B concentrations remained stable and low in the Midwest during week 32. Clinical data continues to show a low influenza illness burden in the Midwest—all states remained in the minimal ILI activity level in week 31. 

COVID-19: SARS-CoV-2 wastewater concentrations increased in the Midwest during week 32 at 857 copies per mL. Michigan, Minnesota, and Ohio are Midwestern states in COVID-NET. In week 31, hospitalization rates decreased in all three states.

The Northeast

RSV: In the Northeast, RSV wastewater concentrations remained stable and very low during week 32.

Influenza: Influenza A concentrations held steady and remained very low in the Northeast during week 32, and after a brief increase, influenza B concentrations are also back down. In week 31, all Northeastern states remained in the Minimal ILI activity level. 

COVID-19: SARS-CoV-2 wastewater concentrations increased in the Northeast during week 32 at 808 copies per mL. Connecticut, Maryland, and New York are Northeastern states in COVID-NET. In week 31, hospitalization rates decreased in Maryland and held steady in Connecticut and New York.

The West

RSV: RSV wastewater concentrations remained stable and very low in the West during week 32.  

Influenza: Influenza A and B concentrations held steady and remained very low in the West during week 32. During week 31, all Western states were at the Minimum ILI activity level. 

COVID-19: During week 32, SARS-CoV-2 wastewater concentrations increased in the West at 613 copies per mL. California, Colorado, New Mexico, Oregon, and Utah are Western states in COVID-NET. In week 31, hospitalization rates decreased in Colorado, New Mexico, and Oregon, held steady in California, and increased in Utah.

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Footnotes: 

Wastewater data from Biobot Analytics for RSV, influenza, and SARS-CoV-2 are through August 10, 2024 (MMWR week 32). Clinical data on testing, hospitalizations, and emergency department visits for RSV, influenza, and COVID-19 are from the Centers for Disease Control and Prevention. Updates to clinical data for RSV, influenza, and COVID-19 are through August 3, 2024 (MMWR week 31).