VIRAL FORECAST DISCUSSION
The most recent week with data shows a mixed pattern of enteric viral activity in wastewater. Several key pathogens, including norovirus genogroup I and II, were detected at levels below their long-term and seasonal averages, while others such as
Sapporo virus and
Astrovirus (other) were present at moderate concentrations, though still below historical norms. Notably,
Kobuvirus aichi was detected at a higher level than its long-term average, and
Adenovirus F41 and
Human mastadenovirus A were present at low concentrations near the assay's detection limit, indicating lower confidence in these measurements. Several pathogens, including rotavirus B and C, and hepatitis A, were not detected in the latest week despite higher recent averages, suggesting a possible decline in circulation. No new pathogens were detected in the latest week that were absent in the previous four weeks.
Noroviruses
Norovirus genogroup II and
Norovirus genogroup I were both detected in the latest week with data, but at levels well below their long-term and seasonal averages. Genogroup II, typically the most common cause of norovirus outbreaks, remains the primary concern for acute gastroenteritis, with transmission occurring via contaminated food, water, surfaces, and person-to-person contact. Genogroup I was present at a higher concentration than its recent 4-week average, but still below historical norms. Symptoms for both genogroups include vomiting, diarrhea, and abdominal cramps, and outbreaks can occur year-round, with peaks in colder months. There is currently no licensed vaccine for norovirus; prevention relies on strict hand hygiene and surface disinfection.
Norovirus genogroup IV was not detected in the latest week, consistent with its typically lower prevalence.
Rotaviruses
Rotavirus A was detected at a low level in the latest week, markedly below its long-term and seasonal averages, and lower than the previous 4-week average. Rotavirus A is a major cause of severe diarrhea in young children and can lead to dehydration and hospitalization. Transmission is primarily fecal-oral, through contaminated hands, surfaces, and food. The low detection suggests limited current circulation.
Rotavirus B and
Rotavirus C were not detected, despite higher recent averages, indicating a possible decrease in activity. Licensed vaccines for rotavirus A are available and recommended for infants to prevent severe disease.
Astroviruses
Astrovirus (other) was present at a moderate level, below both its long-term and seasonal averages, and lower than the recent 4-week average. Astroviruses cause mild to moderate gastroenteritis, primarily in children and immunocompromised individuals, with transmission via the fecal-oral route.
Astrovirus MLB was detected at a low level, near its recent average but below historical norms.
Astrovirus VA was not detected in the latest week.
Sapporo virus
Sapporo virus was detected at a moderate level, below its long-term and seasonal averages but higher than the recent 4-week average. Sapporo virus is associated with sporadic outbreaks of gastroenteritis, primarily in children, and is transmitted via the fecal-oral route.
Kobuvirus aichi
Kobuvirus aichi was detected at a level above its long-term and seasonal averages, but below the recent 4-week average. Kobuvirus aichi is an emerging cause of gastroenteritis, with transmission primarily fecal-oral, and symptoms similar to other enteric viruses.
Adenoviruses
Adenovirus F41 and
Human mastadenovirus A were detected at very low levels in the latest week, near the assay's limit of detection, resulting in lower confidence in these measurements. Adenovirus F41 is associated with pediatric gastroenteritis, while mastadenovirus A is less commonly implicated. Transmission is fecal-oral, and symptoms include diarrhea and fever. No licensed vaccines are available for these enteric adenoviruses.
Other Enteric Viruses
Picobirnavirus was detected at a low level, below its long-term and seasonal averages, and lower than the recent 4-week average. Picobirnavirus is an emerging pathogen with unclear clinical significance, but is associated with gastroenteritis in immunocompromised individuals.
Hepatitis A was not detected in the latest week, despite higher recent averages. Hepatitis A is a vaccine-preventable cause of acute hepatitis, transmitted via contaminated food and water.
Summary and Implications
Wastewater data from the most recent week indicate generally low to moderate circulation of enteric viruses compared to historical and seasonal averages. Norovirus and rotavirus levels remain subdued, but vigilance is warranted, especially in settings with young children and vulnerable populations. Community members should maintain hand hygiene, ensure proper food handling, and stay home when experiencing symptoms of gastroenteritis to reduce transmission. Vaccination against rotavirus and hepatitis A remains the most effective preventive measure for eligible individuals. Continued monitoring of wastewater will provide early warning for potential increases in viral activity.