During the fourth week of 2025, 7,039 cases of acute respiratory illness and influenza were recorded among a surveillance population of 346,739, representing an incidence rate of 203.01 per 10,000 population. The national incidence rate increased compared to the previous week (5 404 cases of acute respiratory diseases and influenza , incidence rate 155.85 per 10 000 population). The incidence reached the level of the same week of the previous season. The overall incidence in all age groups also increased compared to the previous week, particularly marked in young children. The incidence by age group was: 742.88%000 in the 0-4 age group; 647.06%000 in the 5-14 age group; (in week 3 - 580.00%000 in the 0-4 age group; 452.19%000 in the 5-14 age group);
The number of registered cases of ARI and influenza is increasing in almost all district towns, but the epidemic process is of different intensity. With very high epidemic rates in the districts of Blagoevgrad, Varna, Veliko Tarnovo, Vidin, Vratsa, Gabrovo, Dobrich, Kyustendil, Montana, Pernik, Pleven, Plovdiv, Haskovo, Shumen.

With high values, pre-epidemic is the incidence in Burgas, Pazardzhik, Razgrad, Sliven, Stara Zagora, Targovishte. The incidence in Yambol shows a slight decrease.

In Lovech, Ruse, Silistra and Sofia districts, as well as in Kardzhali, Smolyan and Sofia city, the incidence has not yet reached pre-epidemic levels, despite the increasing intensity observed over the last week.

An influenza epidemic has been declared in 11 districts: Varna, Veliko Tarnovo, Vidin, Dobrich, Plovdiv, Haskovo, Yambol, Plovdiv, Vratsa, Shumen and Pleven.

During the week, 603 clinical samples of patients with ARI were tested for influenza A/B and SARS-CoV-2 viruses simultaneously by Real Time PCR at the Influenza and ARI NRL. 68 A(H1N1)pdm09 influenza viruses, 114 A(H3N2)influenza viruses, 69 influenza B/Victoria viruses were detected.

381 clinical specimens of children up to 5 years of age were further tested for 8 non-influenza respiratory viruses. 9 RSV, 2 parainfluenza viruses, 6 adenoviruses and 33 other viruses were detected.