Week 1 review: 1 - 7 January 2024

The weekly retrospective gives a summary of trends in acute respiratory infections, including COVID-19, influenza (influenza virus) and respiratory syncytial virus (RSV).

Trends of the week 

COVID-19: Decrease in the number of cases and the positivity rate of COVID-19.

Respiratory syncytial virus (RSV): Decrease in the number of RSV cases.

Influenza: Slight decrease in the number of influenza cases.

COVID-19 / SARS-CoV-2

From 1 to 7 January 2024 (week 1), the number of people testing positive for SARS-CoV-2 dropped to 240 cases, compared to 338 cases the previous week (-29%).

The positivity rate fell to 14% compared to 20% the previous week. The concentration of viruses detected in wastewater also fell substantially [1].

These indicators suggest that the circulation of SARS-CoV-2 has decreased, which is probably linked to departures during the end-of-year holidays.

The latest sequencing data available for weeks 48-50 show a preponderance of the JN.1 variant (60.9%) (95% CI 52.0-69.8%) followed by the BA.2.86 variant (11.3%) (95% CI: 5.5-17.1%) and the XBB.1.9 variant (10.4%) (95% CI: 4.9-16.2%) [2]. It should be noted that the JN.1 variant is a descendant of the BA.2.86 variant with an additional mutation on its spike protein.

Influenza

For the week of 1 January to 7 January 2024 (week 1), the number of influenza cases reported by laboratories decreased to 332 cases from 371 cases in the previous week, a decrease of 11% compared to the previous week.

These data largely overlap with LNS sentinel surveillance, which indicates high circulation of the influenza virus, followed by SARS-CoV-2, rhinovirus and RSV.

Respiratory syncytial virus (RSV)

For the week of 1 to 7 January 2024 (week 1), the number of respiratory syncytial virus (RSV)-positive individuals reported by laboratories dropped to 52 cases, compared with 77 the previous week, presenting an increase of 32%. The peak of the epidemic this season was reached in week 50, from 11 to 17 December 2023.

[1] https://www.list.lu/en/covid-19/coronastep/

[2] https://lns.lu/publications/