Please see below for the latest update on Merced, Stanislaus, and Yolo County wastewater data.

  • Weeks 100-101: 09/17 - 09/30
  • Weeks 102-103: 10/01 - 10/14

General Update at County Level

For each county, the aggregated trend is population-weighted. It is calculated using the 10-days trimmed average for each site. For each date, an individual site trimmed smoothed value for the day is multiplied by the plant’s population, then these are summed and divided by the total population of all sites.

Table: Percentage of change

Percent change
Virus Merced County Stanislaus County Yolo County
SARS-CoV-2 40.2% 50.8% +12.6%
Influenza A +14.7% +LL 47.2%
Influenza B 40.2% 50.8% +12.6%
RSV +72.7% +LL +125.5%
HMPV 45.3% ND 19.1%
Norovirus 5.5% 26.3% 8.9%
Percent change is calculated here using average of measurements over the past two weeks compared to the average of measurements from the prior two weeks.
ND- Non-detect (below detection limit)
+LL increasing but at low levels
Weeks 100-101: 09/17 - 09/30
Weeks 102-103: 10/01 - 10/14

Current wastewater level

Current wastewater level
Virus Merced County Stanislaus County Yolo County
SARS-CoV-2 Low Low High
Influenza A Medium High Medium
Influenza B Low Low High
RSV High High Medium
HMPV Medium Low Medium
Norovirus Low Low Low
The current wastewater levels are estimated using the 10-day rolling average (10-d.m.a). The 33rd and 66th percentiles are calculated over the past 365 days before 14 days ago. For counties with less than 365 days, all days before 14 days ago are used. The current wastewater level is classified as:
• Low: The current 10-dma is below 33rd percentile
• Medium: The current 10-dma is between the 33rd and 66th percentile
• High: The current 10-dma is above 66th Percentile

Trend test at county level

Relative Strength Index

The Relative Strength Index
Virus Merced County Stanislaus County Yolo County
SARS-CoV-2 Very likely downward Very likely downward No Trend
Influenza A No Trend Likely upward Downward
Influenza B Very likely downward Very likely downward No Trend
RSV Upward Upward No Trend
HMPV No Trend No Data No Trend
Norovirus No Trend Very likely downward Downward
Week 103: 10/01 - 10/14
* The Relative Strength Index (RSI) calculates a ratio of the recent upward price movements to the absolute price movement. Developed by J. Welles Wilder.

Mann-Kendall trend test

Mann-Kendall trend test
Virus Merced County Stanislaus County Yolo County
SARS-CoV-2 Very likely downward Very likely downward Very likely upward
Influenza A Very likely downward Very likely upward Very likely downward
Influenza B Very likely downward Very likely downward Very likely upward
RSV Very likely upward Very likely upward Very likely upward
HMPV Very likely downward No Data No Trend
Norovirus Very likely upward Very likely downward Very likely downward
Week 103: 10/01 - 10/14
* The Mann-Kendall (MK) trend test is a nonparametric test that evaluates whether there is a monotonic trend in a time-series dataset. We applied the MK trend test to raw N/PMMoV data and used a 14-day lookback period. We interpreted positive values of the test statistic, tau (τ), with p ≤ 0.1, p ≤ 0.05, and p ≤ 0.01 as upward, likely upward, and very likely upward trends, respectively. We interpreted negative τ values with p ≤ 0.1, p ≤ 0.05, and p ≤ 0.01 as downward, likely downward, and very likely downward trends, respectively.

Percent change (PC)

Percent change in the last 14 days
Virus Merced County Stanislaus County Yolo County
SARS-CoV-2 Very likely downward Very likely downward Very likely upward
Influenza A Very likely downward Very likely upward Very likely downward
Influenza B Very likely downward Very likely downward Very likely upward
RSV Very likely upward Very likely upward Very likely upward
HMPV Very likely downward No Trend No Trend
Norovirus Very likely upward Very likely downward Very likely downward
Week 103: 10/01 - 10/14
* The slope is calculated from a least-squares linear regression of log10-transformed values of the N/PMMoV data versus day. We used a 14-day look-back period to calculate the slope. For each slope estimate, we extracted the 90%, 95%, and 99% confidence intervals (CIs) to calculate the 90%, 95%, and 99% CIs for each PC estimate. We interpreted PC values greater than 0 for the 90%, 95%, and 99% upper CIs as upward, likely upward, and very likely upward trends, respectively. We interpreted PC values less than 0 for the 90%, 95%, and 99% lower CIs as downward, likely downward, and very likely downward trends day and previous n - 1 days.

Trend and effective reproductive number at county level

The embedded graph shows the effective reproductive number, Rt, which is the expected number of new infections caused by a single infectious person where some individuals may no longer be susceptible. It used to assess whether the epidemic is growing (>1), shrinking (<1), or holding steady (~1). To compute Rt from wastewater data, we utilize a proxy of the cases derived from the smoothed SARS-CoV-2 RNA concentration. The process involves dividing the smoothed concentration by the minimum concentration observed in the treatment plant. This normalization step ensures that the minimum concentration corresponds to a value of \(1\), serving as a reference point. Next, we multiply the normalized concentration by a scalar value, k, which we set as 4. This assumption implies that the minimum concentration observed in the treatment plant corresponds to approximately 4 infected individuals. The choice of k is not critical for calculating since it is scale-free.

The formula for computing the proxy of cases from wastewater data is as follows: \[I_{ww}= k \frac{C_{RNA}}{min {(C_{RNA})}}\] where \(C_{RNA} = (C_1,\ldots,C_n)\) represents the smoothed concentration vector at different time points. By applying this formula, we obtain a proxy of the cases based on the wastewater data.

Merced County

Stanislaus County

Yolo County

General Update at City Level

Table: Percentage of change

Percent change
Virus Merced County Stanislaus County Yolo County
Merced Los Banos Modesto Turlock Davis Esparto Winters Woodland
SARS-CoV-2 46.6% +110.7% 38.2% +81.9% +42% 76.3% +71.1% 38.9%
Influenza A +3468.1% 45.2% +LL +LL 31.4% ND ND 55.3%
Influenza B ND ND ND +LL ND ND ND ND
RSV 9.9% +202.1% +327.8% +127.8% 14.9% ND ND ND
HMPV ND +LL ND ND ND ND ND +127.6%
Norovirus +149.4% +65.5% 31% +39.7% +37.3% +122.5% 75.9% 34.4%
Percent change is calculated here using average of measurements over the past two weeks compared to the average of measurements from the prior two weeks.
ND- Non-detect (below detection limit)
+LL increasing but at low levels
Weeks 100-101: 09/17 - 09/30
Weeks 102-103: 10/01 - 10/14

Current wastewater level

Current wastewater level
Virus Merced County Stanislaus County Yolo County
Merced Los Banos Modesto Turlock Davis Esparto Winters Woodland
SARS-CoV-2 Low Medium Low Low High Low Medium Medium
Influenza A High High Low Low Low Low Low High
Influenza B Low Low Low High Low Low Low Low
RSV High Medium Low Low Low Low Low Low
HMPV Low Medium Low Low Low Low Low High
Norovirus Medium Low Low Low Low Medium Low Low
The current wastewater levels are estimated using the 10-day rolling average (10-d.m.a). The 33rd and 66th percentiles are calculated over the past 365 days before 14 days ago. For cities with less than 365 days, all days before 14 days ago are used. The current wastewater level is classified as:
• Low: The current 10-dma is below 33rd percentile
• Medium: The current 10-dma is between the 33rd and 66th percentile
• High: The current 10-dma is above 66th Percentile

Tab: Trend test at city level

Table 1: Percent change (PC)

Percent change in the last 14 days
Virus Merced County Stanislaus County Yolo County
Merced Los Banos Modesto Turlock Davis Esparto Winters Woodland
SARS-CoV-2 Very likely downward Very likely upward Very likely downward No Trend Upward Likely upward Very likely upward Likely downward
Influenza A No Trend Downward No Trend No Trend Very likely downward No Trend No Trend No Trend
Influenza B No Trend No Trend No Trend No Trend No Trend No Trend No Trend No Trend
RSV No Trend No Trend No Trend Downward Likely downward No Trend No Trend No Trend
HMPV Very likely downward No Trend No Trend No Trend No Trend No Trend No Trend Upward
Norovirus Very likely upward Very likely upward Very likely downward No Trend Very likely upward Very likely upward Very likely downward Very likely downward
Week 103: 10/01 - 10/14
* The slope is calculated from a least-squares linear regression of log10-transformed values of the N/PMMoV data versus day. We used a 14-day look-back period to calculate the slope. For each slope estimate, we extracted the 90%, 95%, and 99% confidence intervals (CIs) to calculate the 90%, 95%, and 99% CIs for each PC estimate. We interpreted PC values greater than 0 for the 90%, 95%, and 99% upper CIs as upward, likely upward, and very likely upward trends, respectively. We interpreted PC values less than 0 for the 90%, 95%, and 99% lower CIs as downward, likely downward, and very likely downward trends day and previous n - 1 days.

Table 2: Relative Strength Index

The Relative Strength Index
Virus Merced County Stanislaus County Yolo County
Merced Los Banos Modesto Turlock Davis Esparto Winters Woodland
SARS-CoV-2 No Trend No Trend Downward No Trend No Trend Downward Upward No Trend
Influenza A No Trend No Trend No Trend No Data No Trend No Data No Data No Data
Influenza B No Data No Data No Data No Data No Data No Data No Data No Data
RSV No Trend No Data No Trend No Trend No Trend No Data No Trend No Data
HMPV No Trend No Data No Data No Data No Data No Data No Data Very likely upward
Norovirus Likely upward No Trend Downward No Trend No Trend No Trend Very likely downward No Trend
Week 103: 10/01 - 10/14
* The Relative Strength Index (RSI) calculates a ratio of the recent upward price movements to the absolute price movement. Developed by J. Welles Wilder.

Table 3: Mann-Kendall trend test

Mann-Kendall trend test
Virus Merced County Stanislaus County Yolo County
Merced Los Banos Modesto Turlock Davis Esparto Winters Woodland
SARS-CoV-2 Likely downward Very likely upward Very likely downward No Trend Upward Likely upward Likely upward No Trend
Influenza A No Trend Likely downward No Trend No Data Very likely downward No Data No Data No Data
Influenza B No Data No Data No Data No Data No Data No Data No Data No Data
RSV No Trend No Data No Trend Likely downward Downward No Data No Trend No Data
HMPV Very likely downward No Data No Data No Data No Data No Data No Data Very likely upward
Norovirus Very likely upward Very likely upward Likely downward No Trend Very likely upward Likely upward Very likely downward Very likely downward
Week 103: 10/01 - 10/14
* The Mann-Kendall (MK) trend test is a nonparametric test that evaluates whether there is a monotonic trend in a time-series dataset. We applied the MK trend test to raw N/PMMoV data and used a 14-day lookback period. We interpreted positive values of the test statistic, tau (τ), with p ≤ 0.1, p ≤ 0.05, and p ≤ 0.01 as upward, likely upward, and very likely upward trends, respectively. We interpreted negative τ values with p ≤ 0.1, p ≤ 0.05, and p ≤ 0.01 as downward, likely downward, and very likely downward trends, respectively.

Merced County

SARS-CoV-2

Merced’s average SARS-CoV-2 concentrations (N/PMMoV) decreased ⬇️ by 46.6% between the most recent two weeks and the two weeks prior to that. Los Banos’ average increased ⬆️ by 110.7%.

Fig 1. Merced

Fig 2. Los Banos

Influenza A

Merced’s average Influenza A concentrations (Flu A/PMMoV) increased ⬆️ by 3468.1% between the most recent two weeks and the two weeks prior to that. Los Banos’ average decreased ⬇️ by 45.2%.

Influenza B

Merced’s average Influenza B concentrations (Flu B/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Los Banos’ average showed no detection.

RSV

Merced’s average RSV concentrations (RSV/PMMoV) decreased ⬇️ by 9.9% between the most recent two weeks and the two weeks prior to that. Los Banos’ average increased ⬆️ by 202.1%.

HMPV

Merced’s HMPV concentrations (HMPV/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Los Banos’s average +LL.

Norovirus

Merced’s average Norovirus concentrations (Norovirus/PMMoV) increased ⬆️ by 149.4% between the most recent two weeks and the two weeks prior to that. Los Banos’ average increased ⬆️ by 65.5%.

Stanislaus County

SARS-CoV-2

Modesto’s average SARS-CoV-2 concentrations (N/PMMoV) decreased ⬇️ by 38.2% between the most recent two weeks and the two weeks prior to that. Turlock’s average increased ⬆️ by 81.9%.

Fig 1. Modesto

Fig 2. Turlock

Influenza A

Modesto’s average Influenza A concentrations (Flu A/PMMoV) +LL between the most recent two weeks and the two weeks prior to that. Turlock’s average +LL.

Influenza B

Modesto’s average Influenza B concentrations (Flu B/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Turlock’s average +LL.

RSV

Modesto’s average RSV concentrations (RSV/PMMoV) increased ⬆️ by 327.8% between the most recent two weeks and the two weeks prior to that. Turlock’s average increased ⬆️ by 127.8%.

HMPV

Modesto’s average HMPV concentrations (HMPV/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Turlock’s average showed no detection.

Norovirus

Modesto’s average Norovirus concentrations (Norovirus/PMMoV) decreased ⬇️ by 31% between the most recent two weeks and the two weeks prior to that. Turlock’s average increased ⬆️ by 39.7%.

Yolo County

SARS-CoV-2

Davis’ average SARS-CoV-2 concentrations (N/PMMoV) increased ⬆️ by 42% between the most recent two weeks and the two weeks prior to that. Esparto’s average decreased ⬇️ by 76.3%. Winters’ average increased ⬆️ by 71.1%. Woodland’s average decreased ⬇️ by 38.9%.

Fig 1. Davis

Fig 2. Esparto

Fig 3. Winters

Fig 4. Woodland

Influenza A

Davis’ average Influenza A concentrations (Flu A/PMMoV) decreased ⬇️ by 31.4% between the most recent two weeks and the two weeks prior to that. Esparto’s average showed no detection. Winters’ average showed no detection. Woodland’s average decreased ⬇️ by 55.3%.

Influenza B

Davis’ average Influenza B concentrations (Flu B/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Esparto’s average showed no detection. Winters’ average showed no detection. Woodland’s average showed no detection.

RSV

Davis’ average RSV concentrations (RSV/PMMoV) decreased ⬇️ by 14.9% between the most recent two weeks and the two weeks prior to that. Esparto’s average showed no detection. Winters’ average showed no detection. Woodland’s average showed no detection.

HMPV

Davis’ HMPV concentrations (HMPV/PMMoV) showed no detection between the most recent two weeks and the two weeks prior to that. Esparto’s average showed no detection. Winters’ average showed no detection. Woodland’s average increased ⬆️ by 127.6%.

Norovirus

Davis’ Norovirus concentrations (Norovirus/PMMoV) increased ⬆️ by 37.3% between the most recent two weeks and the two weeks prior to that. Esparto’s average increased ⬆️ by 122.5%. Winters’ average decreased ⬇️ by 75.9%. Woodland’s average decreased ⬇️ by 34.4%.

All Counties

Mpox Update

There are no detections for samples taken at our plants from the last two weeks. https://healthycvtogether.org/monkeypox-data/