Wastewater Viral Surveillance Discussion
During the most recent week with data, enteric virus activity in wastewater showed notable elevations for several key pathogens compared to both long-term and seasonal averages. Norovirus genogroup I and II levels were substantially higher than typical for this time of year, with genogroup I showing a pronounced spike relative to recent weeks.
Astrovirus (other) also registered at an elevated level, exceeding both historical and recent averages. In contrast,
Rotavirus A remained well below its long-term and seasonal averages, though it was slightly higher than the previous four-week period. Several pathogens, including
Rotavirus B,
Rotavirus C, and
Sapporo virus, were undetectable in the latest sample, continuing a trend of low or absent detection over recent weeks. Some viruses were detected at levels near the assay's limit of detection, indicating lower confidence in those measurements.
Noroviruses
Norovirus genogroup I and
Norovirus genogroup II both showed marked increases in the latest week with data. Genogroup I, in particular, was detected at a much higher level than both its long-term and seasonal averages, as well as the previous four-week average. Genogroup II also rose sharply, with levels well above historical and seasonal norms. Noroviruses are primarily transmitted via the fecal-oral route, often through contaminated food, water, or surfaces. Symptoms typically include acute gastroenteritis with vomiting, diarrhea, and abdominal pain. Norovirus outbreaks are common in winter months, and there is currently no licensed vaccine for general public use. Enhanced hand hygiene and surface disinfection remain the primary preventive measures.
Norovirus genogroup IV was detected at a very low level, near the assay's limit of detection, and confidence in this measurement is reduced. Genogroup IV is less commonly associated with human illness but shares similar transmission routes and symptoms.
Rotaviruses
Rotavirus A was present at a level well below both its long-term and seasonal averages, though slightly higher than the previous four-week average. Rotavirus A is a leading cause of severe diarrhea in young children and is spread via the fecal-oral route. Symptoms include watery diarrhea, vomiting, fever, and abdominal pain. Rotavirus activity typically peaks in late winter and early spring. There are licensed vaccines available for infants that provide strong protection against severe disease.
Rotavirus B and
Rotavirus C were undetectable in the latest week with data, continuing a pattern of low activity over recent weeks. Both viruses are less common in humans and are typically associated with milder or sporadic outbreaks.
Astroviruses
Astrovirus (other) was detected at a notably elevated level, exceeding both long-term and seasonal averages as well as the recent four-week average. Astroviruses are transmitted via the fecal-oral route and primarily cause mild gastroenteritis, especially in young children and immunocompromised individuals. Seasonal peaks often occur in late winter and early spring. There are currently no licensed vaccines for astrovirus.
Astrovirus MLB and
Astrovirus VA were detected at moderate levels, with MLB below its historical average and VA slightly elevated compared to recent weeks.
Sapporo Virus
Sapporo virus was undetectable in the latest week with data, despite higher levels in the previous four-week period. Sapporo virus is transmitted via the fecal-oral route and causes gastroenteritis, particularly in children. There is no vaccine available.
Other Enteric Viruses
Kobuvirus aichi was detected at a very low level, near the assay's limit of detection, and confidence in this result is reduced. Kobuvirus is associated with mild gastrointestinal symptoms.
Adenovirus F41 and
Adenovirus F were present at moderate levels, slightly above their long-term averages. These viruses can cause gastroenteritis, especially in young children, and are spread via contaminated water, food, or surfaces. There is no widely available vaccine for these enteric adenoviruses.
Picobirnavirus was detected at a moderate level, consistent with historical averages. Picobirnavirus is associated with mild gastrointestinal illness and is transmitted via the fecal-oral route.
Hepatitis A was undetectable in the latest week with data, despite higher levels in the previous four-week period. Hepatitis A is a vaccine-preventable disease that causes liver inflammation and is spread via contaminated food or water.
Salivirus was detected at a moderate level, below long-term and seasonal averages but above the recent four-week average. Salivirus is associated with mild gastroenteritis and is transmitted via the fecal-oral route.
Summary and Implications
Wastewater data from the most recent week with data indicate elevated norovirus and astrovirus activity, with norovirus genogroup I and II levels substantially higher than typical for this season. Rotavirus A remains below historical norms, but vigilance is warranted given its potential severity in young children. Community members should be attentive to hand hygiene, especially in group settings and food preparation environments. Parents and caregivers of young children should ensure rotavirus vaccination is up to date. Individuals experiencing symptoms of gastroenteritis should avoid preparing food for others and seek medical attention if symptoms are severe or prolonged. Regular cleaning of shared surfaces and prompt reporting of outbreaks in institutional settings can help limit transmission.