Summary: Week of 6/10/24

We continue to monitor the rapidly 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 23 (June 8) also indicate that influenza activity remains low in the four US regions. We want to highlight are 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 of the upticks we’ve observed are due to seasonal influenza A virus or if H5N1 could be playing a role. 
• Biobot is currently testing for influenza A in 8 out of the 10 states with positive dairy herds (Texas, New Mexico, Kansas, Idaho, Ohio, North Carolina, South Dakota, and Iowa), among several other states across the country. 
• Our current assays do not distinguish between infections in humans versus infected animals that are shedding into the wastewater system. 

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

Biobot’s national wastewater network showed decreasing and very low national concentrations of influenza A & B and RSV during week 23, while SARS-CoV-2 concentrations continued to increase. Nationally, major clinical metrics remained low for influenza, and RSV in week 22, while some metrics for COVID-19 continued to show signs of increase. The percentage of outpatient visits due to influenza-like illness (ILI) continues to stay below the national baseline of 2.9%, currently at 1.9%. While some states did experience increases in ILI-associated outpatient visits in the previous week, the nonspecific nature of the symptoms make it difficult to determine if the increases are due to influenza or an increase in COVID-19 activity. However, overall, the respiratory illness burden remains low.

The Bottom Line: As we head into summer, we are keeping our eyes on two things: 1. Increasing SARS-CoV-2 concentrations which suggests the start of a summer wave, and 2. The evolving H5N1 situation, which thankfully does not currently pose a significant threat to human health. Closely monitoring both these situations is essential to protecting human health. Our recommendations to keep yourself and loved ones healthy remain the same: if you feel unwell, minimize contact with others, consider wearing a mask in crowded areas, and stay current with vaccinations and boosters. Taking these precautions can help keep you and your loved ones healthy.

National Outlook

RSV

Nationally, RSV concentrations remained very low in week 23.

Influenza

Nationally, influenza A and B concentrations continued to decline in week 23 and overall, both remained low. 

Clinical data showed that the illness burden due to influenza held steady in week 22. Test positivity from clinical labs did not change in week 22, currently at 1.8%. The percentage of outpatient visits for influenza-like illness (ILI) – typical in flu, RSV, and COVID-19 patients – also held steady and remains below the national baseline of 2.9%, currently at 1.9%. FluSurv-NET reports that the influenza hospitalization rate per 100,000 persons also remains very low, currently at 0.2 in week 22. These metrics are 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 23. The national average SARS-CoV-2 wastewater concentration is now 368 copies per mL. 

Clinical metrics continued to show some signs of increasing COVID-19 activity in week 22. Test positivity increased, currently at 4.5%. COVID-NET reports that the hospitalization rate per 100,000 persons is currently 1.1 in week 22. Deaths due to COVID-19 held steady, and currently represent 0.6% of all deaths in the US.

Regional

The South

RSV: In the South, RSV wastewater concentrations remained stable and very low during week 23.  

Influenza: Influenza A and B concentrations held steady at very low levels in the South during week 23.  Clinical data continues to confirm that disease burden due to influenza remains low – all Southern states remained in the Minimal ILI activity level through week 22. West Virginia and Mississippi did experience a very small uptick in outpatient visits due to ILI in week 22, while all other Southern states experienced no change or decreased.  

COVID-19: SARS-CoV-2 wastewater concentrations increased in the South during week 23, currently at 278 copies per mL. The two Southern states in COVID-NET, an enhanced hospitalization surveillance system, are Georgia and Tennessee. Georgia experienced a slight decrease in COVID-19 hospitalization rates in week 22, while Tennessee experienced a slight increase. Overall, COVID-19 hospitalization rates in both states remained low.

The Midwest

RSV: RSV concentrations remained stable and very low in the Midwest during week 23.

Influenza: Influenza A and B wastewater concentrations remained stable and very low in the Midwest in week 23. Clinical data continues to show low influenza illness burden in the Midwest – all states remained in the Minimal ILI activity level in week 22. Kansa, however, appears to have experienced some slight increase in outpatient visits due to ILI over the previous two weeks, but levels remained low overall.

COVID-19: SARS-CoV-2 wastewater concentrations increased in the Midwest during week 23, currently at 361 copies per mL. Michigan, Minnesota, and Ohio are Midwestern states in COVID-NET. In week 22, Michigan and Minnesota experienced very small increases in COVID-19 hospitalization rates while Ohio held steady. Overall, hospitalization rates remained low. 

The Northeast

RSV: In the Northeast, RSV wastewater concentrations remained stable and very low during week 23.

Influenza: Influenza A and B concentrations held steady and remained very low in the Northeast during week 23. In week 22, all Northeastern states remained in the Minimal ILI activity level. Delaware and New Hampshire appear to be fluctuating a little more than other Northeast states in terms of outpatient visits due to ILI, but their levels still remain low.

COVID-19: SARS-CoV-2 wastewater concentrations increased in the Northeast during week 23, currently at 430 copies per mL. Connecticut, Maryland, and New York are Northeastern states in COVID-NET. In week 22, Connecticut experienced a decrease in COVID-19 hospitalization rates while New York held steady and Maryland experienced a small increase. Hospitalization rates remained low overall.

The West

RSV: RSV wastewater concentrations remained stable and very low in the West during week 23.   

Influenza: Influenza A and B concentrations held steady and remained very low in the West during week 23. During week 22, all Western states but one are in the Minimal ILI activity level, while California moved from Minimal to Low. Wyoming and Hawaii continued to experience increases in outpatient visits due to ILI. It appears that the West is experiencing some increases in clinical burden due to respiratory illnesses. 

COVID-19: During week 23, SARS-CoV-2 wastewater concentrations increased in the West, currently at 403 copies per mL. In week 22, California was the only Western state in COVID-NET that experienced an increase in hospitalization rates for COVID-19, while Colorado, Oregon, New Mexico, and Utah either held steady or had decreases. Hospitalizations in the West remain low overall.

---

Footnotes: 

Wastewater data from Biobot Analytics for RSV, influenza, and SARS-CoV-2 are through June 8, 2024 (MMWR week 23). 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 June 1, 2024 (MMWR week 22).