Viral load does not remain stable over time. Two main factors explain its degradation:

- The temperature of the wastewater flows

- The duration of the journey through the sewers

In a situation where the wastewater flow is at a temperature of 20°C, at least 25% of the viral load must remain, even in situations where the average travel time in the sewer is long (e.g. 10 h).

Thus, the temperature-adjusted degradation of such a biomarker will not be constant over a year, and instead may vary significantly.