Recent data suggest that monkeypox DNA can also be detected in a variety of body fluids of those infected. This includes respiratory and nasal secretions, spit, urine, faeces and semen, meaning that a tissue washed from someone with smallpox can pick up the virus in sewage.
If the genetic footprint of a pathogen can persist in wastewater for more than 24 hours, it is likely that SCAN can detect it. The viral RNA of Covid-19 persists in wastewater for more than 10 days. Although monkeypox DNA appears to clear the 24-hour threshold, there is no public research on how long it persists.
A question remains as to how much monkeypox DNA needs to get into the sewage for SCAN to actually detect it. SCAN can detect covid in the sewage of as few as two infected people out of 100,000.
Even in a state like California, which keeps sewage and drains separate, rain dilutes the amount of viral DNA in the sewage. To account for this, SCAN normalizes its estimates using a virus with a well-established expected amount: the mild pepper virus. Healthy humans excrete the harmless virus after eating pepper and pepper-based products, making it the most abundant RNA virus in human feces (conveniently, it’s also very stable in water).
There is no evidence that you can contract monkey pox from sewage. According to the World Health Organization, what drives human-to-human transmission is close and prolonged contact with an infected person who directly exposes them to their skin rash, body fluids or respiratory droplets. The bedding and clothing of those with monkeypox can also spread the virus.
Monkey pox has its own vaccine. The smallpox vaccine, which the US has in its national stockpile, also provides protection against smallpox. But public access to monkeypox testing, treatment and vaccines is still limited. Examining wastewater can help public health officials detect outbreaks of monkeypox without widespread testing and determine where to invest resources.
Wastewater monitoring can also detect new variants of monkeypox, two of which are currently circulating in the US. Virtually all of the current outbreak is caused by the West African strain of monkeypox, for which SCAN has a specific test. This strain is more infectious but much less deadly than the other strain, known as the Congo Basin clade. In recent years, monkeypox has killed 3 to 6 percent of those it infects, and is deadliest in young children. Monkey pox has killed three people worldwide this year.
SCAN is currently the only effort to publish data on monkeypox in wastewater. “The Bay Area is at the forefront of wastewater monitoring because we are Silicon Valley after all,” Boehm says. “But it’s not like California has monkeypox in the sewage and nowhere else.”