Number of reported cases of RSV, COVID-19 and flu in 2024-2025; Credit: MSAN

On Thursday 18 December 2025, the Health Directorate of Luxembourg's Ministry of Health and Social Security published its weekly overview on the development of major acute respiratory infections, including COVID-19, influenza (flu) and respiratory syncytial virus (RSV), for the week of Monday 8 to Sunday 14 December 2025 (week 50).

Slight increase in COVID-19 / SARS-CoV-2 cases

During week 50, the number of positive COVID-19 cases increased from 91 to 113, representing a 24% increase compared to the previous week. Furthermore, the viral concentration detected in wastewater also showed an increase. The latest available sequencing data reveal that the XFG variant (40.6%), its sub-variant XFG.3 (23.9%) and the NB.1.8.1 variant (23.9%) are predominant.

Flu cases increase further

The number of flu cases reported by laboratories doubled, rising from 367 to 590 cases (+57%), over one week. Influenza A accounted for 99% of the typed results and influenza B for 1%.

The Ministry of Health and Social Security noted that these figures confirm the start of the seasonal influenza wave is continuing to develop and recalled that vaccination is still available - and is free, starting this year, for children and adolescents under the age of eighteen. The ministry noted that vaccination recommendation primarily concerns people aged 65 and over, who are at the highest risk of flu-related complications.

Increase in RSV cases

The number of RSV cases reported by laboratories saw a 35% increase, with 230 confirmed cases compared to 170 the previous week. Since October 2025, 72% of infections have occurred in children under the age of nine, indicating that the virus mainly affects younger age groups.

The ministry reminded the public of essential barrier measures to help to limit the spread of viruses. These include:

• washing hands regularly with soap and water for at least 30 seconds, thoroughly rubbing palms, fingers, the backs of hands and under the nails;
• covering the mouth and nose with a tissue when coughing or sneezing or using the crook of the elbow if no tissue is available;
• disposing of used tissues immediately in a bin and washing hands afterwards;
• avoiding physical contact such as hugs, kisses and handshakes;
• avoiding crowds and gatherings during the epidemic season;
• staying at home when ill to avoid infecting others;
• ventilating rooms regularly, at least three to four times a day for ten minutes.

EO