Laboratory tests of urban wastewater by the National Wastewater Epidemiology Network show a significant increase in the average viral load in all 12 cities tested from December 27 to January 2, compared to the previous week.
The collected samples showed a huge jump: 516% in Agios Nikolaos in Crete, 342% in Larissa, 290% in Ioannina and 283% in Corfu.
Thessaloniki, Alexandroupoli and Volos also saw three-digit growth: 177%, 158% and 140%, respectively.
In the metropolitan area of Attica, which includes Athens, growth was 95%.
Increases were also found in Xanthi (50%), Patras (45%), Chania (38%) and Heraklion (26%).
Wastewater analysis is believed to provide early warning of impending epidemiological trends.