Norovirus can be accurately tracked in wastewater samples, which can help identify outbreaks and trends, according to a new study based on California wastewater surveillance published in Emerging Infectious Diseases.

Norovirus is one of the leading causes of gastroenteritis in the United States, but surveillance is challenging because many cases are unreported, the authors said. As wastewater surveillance has proved useful and accurate for viral detections, including COVID-19, the researchers assessed its usefulness for norovirus. 

The authors collected wastewater data from December 17, 2022, through December 17, 2023, from 76 California wastewater utilities, as part of the WastewaterSCAN program. 

The authors looked for norovirus viral RNA from wastewater samples and compared findings with Centers for Disease Control and Prevention National Respiratory and Enteric Virus Surveillance System (NREVSS) norovirus test positivity at the national and western US regional level. 

Activity peaked in Southern California in February 

That data was then cross-referenced with California Norovirus Laboratory Network (NLN)–confirmed GII norovirus outbreaks, which are published monthly. 

"We observed positive, statistically significant (p<0.001), moderate-to-strong correlations between California regional and statewide wastewater aggregates and US national and western regional NREVSS test positivity," the authors said. 

The authors said they observed distinct regional patterns to norovirus outbreaks in the state, with activity peaking February 22, 2023, in Southern California, and March 24, 2023, in the San Joaquin Valley.

Given that no other local California norovirus surveillance data are available, wastewater data have been used as a local and leading indicator to support investigations of gastrointestinal illness outbreaks.

"Given that no other local California norovirus surveillance data are available, wastewater data have been used as a local and leading indicator to support investigations of gastrointestinal illness outbreaks," the authors concluded. "Those data have enabled LHDs [local health departments] to more (or less) aggressively pursue investigation and control efforts during gastroenteritis outbreaks, efforts that are time- and resource-intensive for LHDs, the public, and affected establishments."

Carbapenem resistance rates in critically ill hospital patients in Brazil rose during the COVID-19 pandemic and have remained higher than pre-pandemic rates, researchers reported last week in the American Journal of Infection Control.

For the study, researchers retrospectively analyzed data on all critically ill, mechanically ventilated adults admitted to eight Brazilian hospitals from January 1, 2018, to April 30, 2023, stratifying the patients into three periods: pre-surge (January 1, 2018, to March 1, 2020), surge (March 1, 2020, to October 1, 2021), and post-surge (after October 1, 2021). The main outcome was the number of carbapenem-resistant gram-negative bacterial isolates across the three periods. 

Brazil had one of the highest COVOD-19 burdens in the world, and notable increases in carbapenem use in Brazilian hospitals during the early months of the pandemic have previously been reported.

Concerns about resistance rates remaining ‘permanently high’

Of the 9,780 patients included in the study, 3,718 were in the pre-surge, 3,185 in the surge, and 2,247 in the post-surge period. The patients in the pre- and post-surge periods had similar characteristics and outcomes, while the patients in the surge period were younger (median age, 70 vs 74 pre-surge vs 75 post-surge), mainly male (57% vs 48% vs 51%), and had higher rates of mechanical ventilation (7 vs 5 days pre- and post-surge). 

The isolation of carbapenem-resistant gram-negative bacteria increased during the surge (rate ratio [RR], 1.8; 95% confidence interval [CI], 1.5 to 2.2 compared to pre-surge), decreased in post-surge (RR, 0.72; 95% CI, 0.6 to 0.9), and remained higher than pre-surge (RR, 1.3; 95% CI, 1.0 to 1.6). Resistance rates for Pseudomonas aeruginosa fell from 32% to 23% pre- to post-surge, whereas Klebsiella pneumoniae doubled during the surge, 26% to 52%, and remained higher (42%) than pre-surge. 

“In a post-COVID-19 world, with the emergence of new infectious diseases and ongoing challenges posed by existing pathogens, the importance of preserving the effectiveness of antimicrobials cannot be overstated,” the study authors wrote. “It is necessary to coordinate efforts to avoid antimicrobial resistance rates remaining permanently high and to prevent future similar antimicrobial stewardship breakdowns.”

Wastewater surveillance with an H5N1 avian flu probe retrospectively deployed to investigate unseasonably high influenza A in Texas in early 2024 was able to detect the virus 2 weeks before cases were reported and a month before the virus was confirmed, which may have been able to speed the public health response, according to study results presented at IDWeek.

Researchers on the WastewaterSCAN team at Stanford University retrospectively developed and deployed a probe for a biomarker of avian influenza to plants across the United States. WastewaterSCAN monitors the levels of 11 viruses such as SARS-CoV-2 and respiratory syncytial virus (RSV) in 190 municipal wastewater systems three times a week to inform local, regional, and national public health responses.

'Critical' public health tool

The probe detected the biomarker for H5N1 at three Texas treatment plants, with two confirming that animal protein had already left processing facilities such as dairy farms. The researchers then compared the results with clinical data on flu-related healthcare visits.