COVID-19 may be getting the lion's share of media attention in the past few weeks as concentrations of the SARS-CoV-2 virus, which causes the illness, are increasing in wastewater, but three other viruses that can cause serious illness have also been on the rise in the past six weeks, according to an analysis of local wastewater samples.
The wastewater is analyzed by Stanford's Sewer Coronavirus Alert Network (SCAN) to identify parts of viruses' genetic code that are shed in human waste and measure their concentrations. The data helps public health authorities track the prevalence of certain diseases in the population.
Influenza type A, norovirus and respiratory syncytial virus (RSV) are again showing increased activity, and depending on where one lives on the Peninsula, one of these nasty bugs could be the cause of fever, chills, aching, cough, diarrhea and vomiting.
Though the viruses were at their peaks in winter and early spring, awareness that these viruses continue to be present and active is important given that people are gathering for the summer, traveling and more often than not aren't wearing masks. Influenza A, for example, is commonly thought of as a winter disease, yet in some areas is on the rise.
The activity of a particular virus also isn't consistent across the Peninsula. Norovirus is trending upwards in southern San Mateo County, while cases of influenza appear to be highest in Palo Alto. Here's a rough breakdown of the state of the top viruses in local watersheds:
Palo Alto Regional Water Quality Control Plant: Influenza type A, RSV and norovirus Influenza A is at its highest concentration since April, according to wastewater samples taken from the Palo Alto Regional Water Quality Control Plant. It bottomed out between July 18 and July 30, and has now risen to four times the amount that was found on July 16.
RSV, another respiratory illness that can cause prolonged coughing and fever, particularly in children and older adults, had a spike that began on July 24 after bottoming out between July 19 and July 23. After a peak on Aug. 3, concentrations are declining again, according to the wastewater data.
Norovirus, which is highly infectious, can cause severe gastrointestinal illness and is particularly dangerous for elderly people, according to the Centers for Disease Control and Prevention. The virus has remained active throughout the spring and summer, never getting to zero. After the latest rise detected on July 25, the concentration dropped by Aug. 7 to about one third of that, with a slight uptick starting to show again.
Silicon Valley Clean Water: Norovirus dominates At the treatment plant in Redwood City, norovirus concentrations for southern San Mateo County are again rising after a previous wave around mid-July. The virus reached its lowest level in six months on July 26, but since then has steadily risen three times higher as of Aug. 8.
RSV has had multiple spikes in the sewershed starting June 28. The concentrations rose rapidly, then plummeted, then rose and plummeted again four different times through July and early August. The last increase on Aug. 2 was the highest in the last three months. The good news is that, as of Aug. 8, it had dropped to zero.
City of Sunnyvale Water Pollution Control Plant: Influenza is on the rise Concentrations of influenza virus in the wastewater have continued to tick up in the last six weeks, according to the sampling, with a series of waves in the last three months. RSV and norovirus, while showing increased concentrations in late July and early August, appear to be slowly trending downward.
San Jose-Santa Clara Regional Wastewater Facility: Norovirus holds steady While influenza and RSV numbers have declined sharply since late July, norovirus concentrations continue to hold relatively steady, showing the virus is still active in the community.
CODIGA (Stanford): A blip on the graph With the Stanford population at its lowest during the summer, the university's wastewater surveillance shows no detection of influenza and RSV, with only negligible amounts of norovirus.
Mpox virus makes a brief return. Although it made headlines earlier in spring, Mpox, which has been spread through close sexual contact between gay men, hasn't been detected in wastewater for months, until recently. Still, its appearance was brief. In Palo Alto wastewater, it was present in July 21 samples in moderate concentrations; also in late July, it was present in high concentrations in Sunnyvale's sewage.
