The reported cases of monkeypox are dropping, can its presence in wastewater help us monitor spread?
The cases of Monkeypox seem to be plateauing off. Case numbers worldwide have dropped to about 700 cases a day from 1000 cases a day a few weeks ago .
For all practical purposes the situation seems under control.
There is a concern that an outbreak may be brewing underground – as the virus has now spread to over 98 countries, 91 of which have not reported cases of Monkeypox before the 2022 outbreak.
The detection of Monkepox virus in the wastewater of urban areas in 4 countries, suggests that this may be a way to track the virus.
Are we missing a potential outbreak?
There is some stigma associated with the current outbreak as it initially expanded in a network of men who have sex with men. Even though it is clear that anyone can get Monkeypox – and close intimate contact is essential for spread. In many cultures, this would make people less likely to get tested.
The disease is also self-limiting – most people recover within 1-3 weeks, although some studies have suggested that a significant fraction need medical care. The disease is painful but mortality is relatively rare (1-10%). So people may be tempted to wait it off rather than present for testing – as tests are not easily accessible.
Cases will therefore be under counted and under-reported.
The recent reports of people who test positive without any symptoms and the possibility of human-animal and animal-human transmission is likely to make it harder to know the true burden in the community.
How then do we keep track of what is really happening?
Wastewater Surveillance is useful when it becomes hard to detect human cases
One way to do this is environmental surveillance, in particular wastewater surveillance. Wastewater surveillance across the world has been set up in the past to track viruses like polio.
These systems have been strengthened and activated to track SARS-CoV-2 outbreaks. It is a particularly useful method to know what is circulating in the community, as human testing drops due to inaccessibility of tests or reluctance to get tested.
Monkeypox virus DNA has been detected in wastewater in four countries
Early reports from four countries suggest that the Monkeypox virus can be detected in the sewage system, it tracks with the detection of cases and can therefore serve as a way of keeping a check on the virus. It may even be possible to locate an outbreak and check the spread using waste water viral loads as an indicator.
Reports from USA, France, Netherlands and Italy suggest that current methodologies used for detection of SARS-CoV-2 in waste water can be leveraged to track Monkeypox. Two of these studies have also looked at transport hubs/airports as potential spots for detection.
Existing wastewater surveillance programs can contribute to surveillance of Monkeypox
This is a relatively low cost system as a single sample can provide information on a large number of people/cover a large area. Ongoing wastewater surveillance programs across the world can be routed to contribute to surveillance of Monkeypox in areas where clinical cases have been detected.
CDC U. 2022 Monkeypox Outbreak Global Map [Internet]. [cited 2022 Aug 24]
ECDC. Joint ECDC-WHO Regional Office Europe Monkeypox Surveillance Bulletin [ 2022 Aug 24]
De Baetselier I, Van Dijck C, Kenyon C, Coppens J, Michiels J, de Block T, et al. Retrospective detection of asymptomatic monkeypox virus infections among male sexual health clinic attendees in Belgium. Nat Med. 2022 Aug;
WHO. Monkeypox Fact Sheet, WHO [cited 2022 Aug 24].
Lapa D, Carletti F, Mazzotta V, Matusali G, Pinnetti C, Meschi S, et al. Comment Monkeypox virus isolation from a semen sample collected in the early phase of infection in a patient with prolonged seminal viral shedding. 2022;
Antinori A, Mazzotta V, Vita S, Carletti F, Tacconi D, Lapini LE, et al. Epidemiological, clinical and virological characteristics of four cases of monkeypox support transmission through sexual contact, Italy, May 2022. Eurosurveillance. 2022;27(22).
Peiró-Mestres A, Fuertes I, Camprubí-Ferrer D, Marcos MÁ, Vilella A, Navarro M, et al. Frequent detection of monkeypox virus DNA in saliva, semen, and other clinical samples from 12 patients, Barcelona, Spain, May to June 2022. Eurosurveillance. 2022;27(28).
Rheinbaben F v., Gebel J, Exner M, Schmidt A. Environmental resistance, disinfection,
and sterilization of poxviruses. In: Poxviruses. 2007.
monkeypox viral DNA in a routine wastewater monitoring program
Marlene K. Wolfe, Dorothea Duong, Bridgette Hughes, Vikram
Chan-Herur, Bradley J. White, Alexandria B. Boehm
(PREPRINT)First detection of Monkeypox virus genome in sewersheds in France
Sebastien Wurtzer, Morgane Levert, Eloise Dhenain, Mickael Boni, Jean Nicolas Tournier, Nicolas Londinsky, Agnès Lefranc, Obepine SIG, Olivier Ferraris, Laurent Moulin medRxiv 2022.08.18.22278938
(PREPRINT) de jonge, Eline and Peterse, Céline and Koelewijn, Jaap and van der Drift, Anne-Merel and van der Beek, Rudolf and Nagelkerke, Erwin and Lodder, Willemijn, The Detection of Monkeypox Virus DNA in Wastewater Samples in the Netherlands. (July 14, 2022).
(PREPRINT) Detection of Monkeypox virus DNA in the wastewater of an airport in Rome, Italy: expanding environmental surveillance to emerging threats G La Rosa, P Mancini, C Veneri, G Bonanno Ferraro, L Lucentini, M Iaconelli, E. Suffredini medRxiv 2022.08.18.22278932