A new COVID-19 subvariant called NB.1.8.1 — nicknamed "Nimbus" — has become the dominant strain circulating in the United States, accounting for an estimated 43% of COVID cases as of late June 2026 according to CDC genomic surveillance data. Multiple states are reporting "high" or "very high" COVID viral levels in wastewater, concentrated in the South and West.
Wastewater surveillance detects COVID viral particles in sewage before those infections are reflected in clinical test counts or hospital data — typically providing a one- to two-week early warning of rising community transmission. For high-risk individuals in the states listed above, the wastewater signal represents an early warning, not yet a clinical surge. Acting on it now offers the best window to prepare.
