📄 infectious diseases

RSV concentration in wastewater and trends among incident hospitalizations in children and older adults

This study demonstrates that wastewater-based epidemiology is a reliable surveillance tool for respiratory syncytial virus (RSV) that correlates strongly with hospitalization trends, offering a three-week lag for children and a two-week early warning for older adults, with wastewater data explaining 88% of the variance in hospital admissions for the over-50 population.

Original authors: Hill, D. T., Laplante, J., Byun, S., Alazawi, M., Gowie, D. L., Biswas, S., Hill, L., Zhu, Y., Foote, M., Kappus-Kron, H., Blatz, M. N., Bradley, I., Ye, Y., St. George, K., Larsen, D. A.

Published 2026-07-23

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Hill, D. T., Laplante, J., Byun, S., Alazawi, M., Gowie, D. L., Biswas, S., Hill, L., Zhu, Y., Foote, M., Kappus-Kron, H., Blatz, M. N., Bradley, I., Ye, Y., St. George, K., Larsen, D. A.

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine the city as a giant, living organism with a massive, hidden bloodstream: the sewer system. While we usually think of sewers as just carrying away waste, scientists have discovered they are actually a treasure trove of information about what's happening inside the community. This field is called "wastewater-based epidemiology." Think of it like a giant, communal health check-up where, instead of asking every single person how they feel, scientists take a sip of the city's "blood" to see what viruses are floating around. It's a way to spot trouble before it becomes a crisis, acting as an early warning system for diseases that spread through the air, like the flu or the common cold. One such virus is Respiratory Syncytial Virus, or RSV. You might know it as a nasty bug that makes babies and older adults very sick, often landing them in the hospital. For a long time, we've had to wait for people to get sick and go to the doctor to know how bad an RSV season is. But what if we could see the virus coming in the sewers before the hospitals get crowded? That's the big question this study tackles: Can the city's "blood" tell us when RSV is about to hit our most vulnerable neighbors?

The researchers in this study decided to play detective with the sewers of four counties in New York State. They collected thousands of samples of wastewater—2,662 of them, to be exact—between September 2022 and July 2024. Using a super-sensitive tool called digital PCR (think of it as a high-tech microscope that counts individual virus particles), they measured how much RSV was swimming in the water. Then, they compared these numbers to the actual number of people who ended up in the hospital with RSV, splitting the data into two groups: kids under 10 and adults over 50.

Here is where the story gets really interesting. The scientists found that the amount of RSV in the wastewater was a very reliable mirror of what was happening in the hospitals. When the virus levels in the sewage went up, the number of hospital admissions went up, too. The correlation was strong, with the numbers matching up very closely. But the real magic happened when they looked at when the signals appeared.

For the kids under 10, the wastewater signal actually lagged behind the hospitalizations by about three weeks. It's as if the kids got sick, went to the hospital, and only a few weeks later did the virus levels in the sewers peak. This suggests that children are often the first to catch the virus and spread it around. However, the plot thickened for the adults over 50. For this group, the wastewater signal was a true crystal ball. The virus levels in the sewers rose up to two weeks before the number of older adults being hospitalized started to climb.

The study suggests that this happens because the virus spreads in a chain reaction. Children get infected first, shedding the virus into the sewers. As the season progresses, they pass it on to the adults around them. By the time the older adults start getting sick enough to need hospital care, the wastewater is already buzzing with high levels of the virus from the earlier wave of infections. Because of this, the researchers found that wastewater data could explain 88 percent of the changes in hospital admissions for people over 50.

In short, this paper suggests that wastewater surveillance is a powerful tool, but its superpower depends on who you are watching. It doesn't give an early warning for the kids (who get sick first), but it acts as a fantastic "two-week head start" alert for the older population. This means that public health officials could potentially use sewage data to prepare hospitals and protect senior centers before the wave of older patients arrives. While the study notes that the virus doesn't always show up in the sewers as early as some other diseases might, and that the data needs to be interpreted carefully, the results strongly suggest that looking at the city's wastewater can give us a crucial head start in protecting our most vulnerable neighbors from RSV.

Technical Summary: RSV Concentration in Wastewater and Trends Among Incident Hospitalizations in Children and Older Adults

Problem Statement
Respiratory Syncytial Virus (RSV) is a seasonal pathogen causing significant morbidity and mortality, particularly in children under two and adults over 50. While clinical surveillance exists, gaps remain because RSV is not a reportable disease in many jurisdictions, and clinical data often suffer from reporting delays. Furthermore, existing wastewater-based epidemiology (WBE) studies have rarely distinguished between pediatric and adult infections, despite the distinct transmission dynamics and severity profiles of these subpopulations. This study addresses the need to validate wastewater surveillance as a tool for monitoring RSV burden and determining its utility as an early warning system for specific high-risk age groups.

Methodology
The researchers analyzed 2,662 influent wastewater samples collected from 24 treatment plants across four New York counties (Erie, Jefferson, Onondaga, and Westchester) between September 2022 and July 2024.

Sample Processing: Two concentration methods were employed: ultracentrifugation (Quadrant Biosciences) for Jefferson, Onondaga, and Westchester counties, and Nanotrap® particles (University at Buffalo) for Erie County. Nucleic acid extraction was performed using Qiagen and MagMAX kits.
Quantification: A multiplexed digital RT-PCR (dRT-PCR) assay targeting the matrix gene of RSV (types A and B) was developed and validated at the Wadsworth Center. The assay demonstrated high specificity with no cross-reactivity against other respiratory viruses and a limit of detection of 10 gene copies/µL for RSV.
Clinical Data Integration: Wastewater data were compared against:
- Case Data: Reported RSV tests from the National Respiratory and Enteric Virus Surveillance System (NREVSS) for Jefferson and Onondaga counties.
- Hospitalization Data: Statewide Planning and Research Cooperative System (SPARCS) records, geocoded to sewersheds and aggregated by county. Hospitalizations were stratified into "all ages," "under 10 years," and "over 50 years."
Statistical Analysis: Spearman's rank correlation was used to assess relationships between wastewater concentrations and clinical metrics. Time-lag analyses were conducted to determine if wastewater signals preceded or followed clinical reports. Predictive Generalized Linear Mixed Models (GLMM) were fitted to forecast hospitalizations in the over-50 population using wastewater data and under-10 hospitalization data as predictors.

Key Results

Detection and Correlation: RSV was consistently detectable in wastewater, with detection rates ranging from 17.8% to 41.1% across sites, peaking during respiratory seasons. Wastewater concentrations showed strong positive correlations with RSV hospitalizations (Spearman's $\rho$ between 0.52 and 0.85, $P < 0.001$ ).
Age-Stratified Lag Dynamics: A critical finding was the divergence in temporal relationships based on age:
- Children (<10 years): Wastewater concentrations lagged behind hospitalizations by an average of three weeks.
- Older Adults (>50 years): Wastewater concentrations acted as a leading indicator, preceding hospitalizations by up to two weeks.
Predictive Power: In predictive models for the over-50 population, wastewater concentration alone explained 88% of the variance in hospital admissions (Efron $R^2 = 0.88$ ) with a two-week lag. The model remained significant even when controlling for under-10 hospitalization trends.
Accuracy: The sensitivity of wastewater detection to predict a concurrent RSV hospitalization was approximately 84%, with specificity around 89%.

Significance and Claims
The authors claim that wastewater-based epidemiology is a reliable surveillance method for RSV that can fill gaps in clinical reporting, particularly where RSV is not a reportable disease. The study's primary contribution is the demonstration that wastewater signals provide an early warning specifically for increases in RSV hospitalizations among older adults, a population where RSV is often under-recognized and under-reported.

The authors posit that the observed lag dynamics reflect the transmission cycle: children are infected first and shed the virus, leading to a rise in wastewater concentrations. This community-wide prevalence then precedes the infection and subsequent hospitalization of older adults. Consequently, wastewater data can serve as a proactive tool for public health agencies to anticipate surges in severe disease among the elderly, potentially allowing for targeted interventions in high-density senior settings such as nursing homes and senior centers. The paper concludes that while RSV wastewater signals do not offer the same early warning for pediatric cases as they do for adults, they are a robust candidate for forecasting adult hospitalization burdens.

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