Great efforts have been made to minimise spread and prevent outbreaks of COVID-19 in hospitals. However, there is uncertainty in identifying nosocomial vs community-acquired infections. To minimise risks and evaluate measures, timely data on infection risk in healthcare institutions are required.

To design an automated nationwide surveillance system for nosocomial COVID-19 using existing data to analyse the impact of community infection rates on nosocomial infections, to explore how changes in case definitions influence incidence and to identify patients and wards at highest risk and effects of SARS-CoV-2 variants.

We used data from the Norwegian real-time emergency preparedness register (Beredt C19), which includes all patients nationwide admitted to Norwegian hospitals between March 2020 and March 2022 with a positive SARS-CoV-2 PCR test during their hospital stay or within 7 days post-discharge. COVID-19 cases were assigned to categories depending on the time between admission and testing.

Infection rates for definite/probable nosocomial COVID-19 increased from 0.081% in year 1 to 0.50% in year 2 in hospital admissions 7 days or longer. Varying the definitions resulted in large changes in registered nosocomial infections. Infection rates were similar across different ward types. By 2022, 58% of patients with a definite/probable nosocomial infection had received three vaccine doses.

Automated national surveillance for nosocomial COVID-19 is possible based on existing data sources. Beredt C19 provided detailed information with only 5% missing data on hospitals/wards. Epidemiological definitions are possible to standardise, enabling easier comparison between regions and countries.

Mycobacterium caprae is a member of the Mycobacterium tuberculosis complex (MTBC) not routinely identified to species level. It lacks specific clinical features of presentation and may therefore not be identified as the causative agent of tuberculosis. Use of whole genome sequencing (WGS) in the investigation of a family microepidemic of tuberculosis in Almería, Spain, unexpectedly identified the involvement of M. caprae.

We aimed to evaluate the presence of additional unidentified M. caprae cases and to determine the magnitude of this occurrence.

First-line characterisation of the MTBC isolates was done by MIRU-VNTR, followed by WGS. Human and animal M. caprae isolates were integrated in the analysis.

A comprehensive One Health strategy allowed us to (i) detect other 11 M. caprae infections in humans in a period of 18 years, (ii) systematically analyse M. caprae infections on an epidemiologically related goat farm and (iii) geographically expand the study by including 16 M. caprae isolates from other provinces. Integrative genomic analysis of 41 human and animal M. caprae isolates showed a high diversity of strains. The animal isolates’ diversity was compatible with long-term infection, and close genomic relationships existed between isolates from goats on the farm and recent cases of M. caprae infection in humans.

Zoonotic circulation of M. caprae strains had gone unnoticed for 18 years. Systematic characterisation of MTBC at species level and/or extended investigation of the possible sources of exposure in all tuberculosis cases would minimise the risk of overlooking similar zoonotic events.

The exact epidemiology of tick-borne encephalitis virus (TBEV) infections is unknown because many TBEV infections have an influenza-like or asymptomatic course. Surveillance data are based on patients with any (predominantly neurological) symptoms that prompted diagnostic testing. Infection- and vaccine-induced antibodies against TBEV can be distinguished using an NS1 IgG ELISA.

In a seroprevalence study we aimed to investigate TBEV antibody prevalence, incidences, manifestation indices and potential protection rates in a highly endemic district in south-western Germany.

We analysed 2,220 samples from healthy blood donors collected between May and September 2021. The reported number of TBEV infections was provided on a sub-district level by the local public health authorities. Blood samples were first screened using a TBEV IgG ELISA. In a second step, all positive samples were further analysed with a recently established NS1 IgG ELISA. The presence of specific antibodies against TBEV (excluding cross-reacting antibodies against other flaviviruses) was confirmed by testing screening-positive samples with a microneutralisation assay.

Of 2,220 included samples, 1,257 (57%) tested positive by TBEV IgG ELISA and 125 tested positive for infection-induced TBEV NS1 antibodies, resulting in a TBEV NS1 IgG seroprevalence at 5.6% in our population. The yearly incidence based on the NS1 ELISA findings resulted in 283 cases per 100,000 inhabitants.

Using the TBEV NS1 IgG assay, we confirmed a manifestation index of ca 2% and a high incidence of predominantly silent TBEV infections (> 250/100,000/year), which exceeds the incidence of notified cases (4.7/100,000/year) considerably.