Summary: Week of 4/29/24

We want to share the information that we have at the moment on the rapidly evolving H5N1 influenza virus situation. 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). While we are not seeing a widespread increase across the country in influenza A virus in the recent week, we are seeing a slight uptick in influenza A concentrations in the South. While this is concerning, we want to highlight some important points about the role of Biobot’s wastewater data in understanding the current circulation/risk of H5N1 in the South and nationally: 

• At this point, we cannot determine if these upticks are due to seasonal influenza A virus or if H5N1 could be playing a role in the increase. 
• Biobot is currently testing for influenza A in 6 of the 9 states with positive dairy herds (Texas, New Mexico, Kansas, Idaho, Ohio, and North Carolina), 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 monitor H5N1 closely. 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 declining national concentrations of SARS-CoV-2, influenza A & B, and RSV during week 17. Nationally, all major clinical metrics declined for COVID-19 and influenza during week 16, while clinical metrics for RSV showed that the burden remains quite low. The percent of outpatient visits due to influenza-like illness (ILI) finally dropped below the national baseline of 2.9% in week 14 and has remained below the threshold in week 16, currently at 2.3%. Nationally, it appears that we are at the tail end of the respiratory season. While this is great news, we have observed recent fluctuations in influenza A wastewater concentrations in the South that will be important to pay attention to in light of H5N1 activity (more details below). It is imperative that we continue to pay close attention to wastewater and clinical data and take note of any changes. Wastewater data will be particularly important to understanding community viral activity moving forward, as national requirements for reporting hospitalizations due to COVID-19 and influenza ended on May 1st, 2024.

The Bottom Line: As we address the evolving H5N1 situation, leveraging every public health tool, including wastewater monitoring, is crucial for staying ahead of potential public health threats. It is important to understand that, currently, H5N1 does not pose a significant risk to human health. However, closely monitoring this situation is essential. 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

National RSV wastewater concentrations continued to decrease in week 17 (through April 27th) and are currently at the lowest levels we’ve observed since we began RSV testing in late October. National clinical RSV metrics continued to remain quite low during week 16.

Influenza

Nationally, influenza A concentrations held steady in week 17 but remained low. We are continuing to keep a very close eye on influenza A concentrations as the highly pathogenic avian influenza virus (HPAI) H5N1 is an influenza A virus subtype that our assay picks up. Right now, we don’t see any national increases in influenza A, which is good news. Nationally, influenza B concentrations continued to decline in week 17. 

Clinical data showed that the illness burden due to influenza continued to decline in week 16, with major metrics continuing to trend downward. The number of hospitalizations due to flu decreased, with a little over 2,700 hospitalizations occurring in week 16. Test positivity from clinical labs also decreased, going from 5.9% to 4.8%. The percentage of outpatient visits for influenza-like illness (ILI) – typical in flu, RSV, and COVID-19 patients – continued to drop and remains below the national baseline of 2.9%, currently at 2.3%. The national baseline is determined by examining influenza-like illness outpatient visits during non-influenza weeks (roughly late spring to late summer when influenza transmission is very low) for the previous two years.

COVID-19

Wastewater data show that COVID-19 activity and community viral load continued to decline during week 17, remaining at the lowest concentrations we’ve observed during this winter surge. As of week 17, the national SARS-CoV-2 wastewater concentration average is 198 copies/mL. 

Clinical metrics continued to show that COVID-19 disease burden decreased nationally in week 16. COVID-19 hospitalizations dropped from around 6,400 in week 15 to around 5,600 in week 16. Test positivity began declining again in week 16, currently at 3%. Deaths due to COVID-19 continued to decline in week 16, and currently represent 0.9% of all deaths in the US.

Regional

The South

RSV: In the South, RSV wastewater concentrations remained very low during week 17. Concentrations are currently the lowest values we’ve observed for the region since we began testing. 

Influenza: Continuing recent trends, influenza B concentrations decreased in the South during week 17. We did observe, however, an increase in influenza A concentrations in the South during week 17.  While we have observed some fluctuations in influenza A concentrations throughout the season, we are paying close attention to what’s going on in the South right now in light of the evolving H5N1 avian influenza situation. Our influenza A assay detects H5N1. However, it does not provide the information needed to distinguish between influenza A subtypes, for example, H5N1 versus H1N1. At this point, we cannot confirm if this uptick we see in the South is being driven by H5N1 or seasonal influenza A. Clinical data, however, continues to show good signs of low disease burden –  all states in the South experienced a decrease in outpatient visits due to ILI during week 16, and all Southern states remain in the Minimal ILI activity level. We will keep a close eye on this evolving situation, continue to work with local public health authorities in the South and across the country, and will provide updates as we obtain more information. 

COVID-19: SARS-CoV-2 wastewater concentrations declined in the South during week 17, currently at 122 copies/mL. Most states in the South experienced a decrease in hospitalizations due to COVID-19 in week 16, with the exception of West Virginia, which experienced an increase.

The Midwest

RSV: RSV wastewater concentrations decreased in the Midwest during week 17 and are currently the lowest values we’ve observed for the region since we began testing.  

Influenza: Wastewater concentrations for influenza A and B decreased in the Midwest during week 17. Concentrations for influenza A are some of the lowest we’ve observed in the region since we began testing, while influenza B concentrations remain slightly elevated but continue to come down. Most states in the Midwest experienced a decrease in outpatient visits due to IL in week 16. However, Iowa experienced a small increase. In week 16, North Dakota moved from the High activity level to the Moderate level, and all other Midwest states remained in the Minimal or Low levels. 

COVID-19: SARS-CoV-2 wastewater concentrations declined in the Midwest during week 17, currently at 192 copies/mL. During week 16, most states in the Midwest experienced a decrease in COVID-19 hospitalizations, with only two (Kansas and Wisconsin) experiencing increases.

The Northeast

RSV: In the Northeast, RSV wastewater concentrations continued to decline in week 17 and are currently the lowest values we observed for the region since we began testing.  

Influenza: Influenza A and B wastewater concentrations both continued to decrease in the Northeast during week 17. Concentrations for influenza A are similar to what they were in early November, and concentrations for influenza B are similar to what they were in December. Most states in the Northeast experienced a decrease in the percent of outpatient visits due to ILI in week 16, with exceptions including Vermont and Rhode Island which experienced small increases. In great news, all Northeastern states are now in the Low or Minimal ILI activity levels. 

COVID-19: SARS-CoV-2 wastewater concentrations declined in the Northeast during week 17, currently at 287 copies/mL. Almost all states in the Northeast experienced decreases in hospitalizations due to COVID-19 in week 16, except Maine, which experienced an increase. 

The West

RSV: RSV wastewater concentrations remained low in the West during week 17 and are currently the lowest values we’ve observed for the region since we began testing.  

Influenza: Wastewater concentrations for influenza A remained stable and very low in the West during week 17 and are at similar levels to those observed when we began testing in late October. Influenza B concentrations slightly increased in week 17 and are similar to levels observed in February. During week 16, almost all states in the West experienced decreased outpatient visits due to ILI or held steady. The exception to this was Montana, which experienced a slight increase in ILI outpatient visits. After some fluctuations in ILI activity over the past couple of weeks, the great news is that all Western states are now at low or minimal ILI activity levels, signaling that influenza activity has declined.

COVID-19: During week 17, SARS-CoV-2 wastewater concentrations slightly declined in the West, currently at 149 copies/mL. While clinical disease burden continues to fluctuate in the West, the most recent week saw more states reporting decreases in hospitalizations than the week prior. During week 16, most states in the west experienced decreases in hospitalizations due to COVID-19, with only three states, including Washington, Nevada, and Utah,  experiencing increases. 

Footnotes: 

Wastewater data from Biobot Analytics for RSV, influenza, and SARS-CoV-2 are through April 27, 2024 (MMWR week 17). 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 April 20, 2024 (MMWR week 16).