Monkeypox has been detected in 10 out of 11 sewersheds that Stanford researchers are studying, including Palo Alto, Sunnyvale, San Jose, Gilroy, Stanford, Silicon Valley Clean Water (in San Mateo County), Davis, Sacramento and two sewersheds in San Francisco, according to the data. Only the University of California, Davis watershed has come up negative thus far.
Monkeypox is a rare virus that causes fever, headache, muscle aches and backache, swollen lymph nodes, chills, exhaustion and a pimple-like itchy or painful rash on the face, inside of the mouth and on other parts of the body. The rash goes through different stages and a person remains contagious until the rash dries up and disappears. The illness typically lasts two to four weeks, according to the Centers for Disease Control and Prevention.
The virus is related to smallpox but it is not the same as chickenpox, according to the CDC. It is spread by close contact, and in particular by sexual activity. Recent cases have been among men who were intimate with other men, although it isn't considered a sexually transmitted disease, according to the CDC.
The SCAN team is collecting the DNA that's part of the virus, not the live, infectious viruses, said Alexandria Boehm, professor at Stanford's Department of Civil and Environmental Engineering, which jointly runs the SCAN project with Emory University.
Palo Alto's sewershed, which serves Palo Alto, Mountain View, East Palo Alto, Los Altos and Los Altos Hills, showed detectable levels of DNA starting July 15 and its highest spike so far on July 17. It again was showing a rise as of July 20, according to the data.
The Silicon Valley Clean Water sewershed, which serves the cities of Belmont, San Carlos, Redwood City and the West Bay Sanitary District, showed the presence of monkeypox on July 21. Codiga (Stanford), which is part of the Palo Alto sewershed, showed the virus DNA on July 19, and Sunnyvale DNA detections on July 9 and July 17.
The San Francisco, Sacramento and San Jose sewersheds have been the hot spots, according to the data.
The presence of monkeypox in Santa Clara County also is corroborated by the Santa Clara County Public Health Department. As of July 26, the county confirmed 39 cases, according to its online dashboard.
It's likely monkeypox DNA will be present in wastewater of other large metropolitan areas, Boehm said.
Given SCAN's experiences working with wastewater for successful surveillance for RSV and influenza, as well as COVID-19 and its variants, Boehm said it's not surprising that an emerging pathogen target like monkeypox DNA is appearing in the wastewater.
"It is encouraging to have evidence that this tool (wastewater surveillance) can provide community-level information on the spread of monkeypox," she said in an email on Monday.
"At the present time, we cannot say how many cases are in the sewersheds with positive detections except to say when we have detected monkeypox DNA it indicates there is at least one person in the sewershed using the sewerage collection system. It will be useful to look at trends in the concentrations as we collect more data and compare those with trends in reported MPX (monkeypox) cases."
On July 23, the World Health Organization declared monkeypox a global health emergency. As of July 25, there are 16,836 confirmed cases worldwide and 3,487 in the United States, according to the CDC. California is the second top state with 356 cases; it is only surpassed by New York, which has 990 cases.
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