Tuberculosis 2022

Tuberculosis - 2022 Report on Disease Occurrence

• 2022 saw a total of 232 notified cases of tuberculosis (TB) in Denmark, which is largely in line with the number recorded since 2020. In the ten preceding years, a continued reduction had been observed in the number of TB cases recorded in Denmark.

• The TB incidence in Denmark was 3.9 cases per 100,000 inhabitants, but the regional incidence varied from 4.8 per 100,000 inhabitants in the Capital Region of Denmark to 1.5 per 100,000 inhabitants in Region Zealand.

• 25% of the TB cases occurred in individuals of Danish origin, whereas 75% occurred in individuals of non-Danish origin.

• The median age was 59 years for individuals of Danish origin and 42 years for individuals of non-Danish origin. Among individuals of Danish origin, the highest case number was observed in the age group 60-69 years, whereas the largest number of cases among individuals of non-Danish origin was seen in the age group 30-39 and 50-59 years of age. Pulmonary TB remains the most frequent presentation (76%), whereas extrapulmonary forms of TB continue to be more frequent among individuals of non-Danish origin.

• Based on the notifications, a total of 96 cases (41%) became infected in Denmark, whereas 122 cases (53%) were infected abroad; and for 14 cases (6%), the country of infection remains unknown.

• Compared with 2021, 2022 recorded an unchanged high share of microscopy-positive pulmonary TB patients (65-69% among individuals of Danish origin), which is substantially higher than before the COVID-19 pandemic (42%). Microscopy-positivity indicates subsequent diagnostics and leads to additional transmission of the infection.

• A total of seven cases of multiple resistant (MDR) tuberculosis were detected. This constitutes an increase compared with the previous year when only one case of “extremely resistant” (XDR) tuberculosis was detected. Additionally, Statens Serum Institut (SSI) has knowledge of another five cases of MDR-TB that were diagnosed abroad and in which treatment was initiated before the patients arrived to Denmark.

• A slight decrease was observed in the number of TB cases belonging to the infection chain coined “Cluster 2”, but the share accounted for by the two main infectious chains in Denmark is approx. 30%, which means that active transmission does occur.

2022 saw a total of 232 notified cases of TB, including 154 men and 78 women. The median age for new cases was 47 years for males (range: 0-91 years) and 38 years for females (range 6-85 years).

In the 2020-2022 period, the incidence has remained largely unchanged. In the previous decade, the TB occurrence declined continuously, but a relatively higher decline was observed in 2020 than in the preceding years. This decline was probably associated with a lull in the number of tests and clinical notifications compared with before the COVID-19 pandemic, Figure 1.

National and regional TB occurrence in 2022

In 2022, the total incidence of TB (number of new cases per year) in Denmark was 3.9 cases per 100,000 inhabitants. The Capital Region of Denmark remains the region to record the highest incidence (4.8 per 100,000) and Region Zealand the lowest (1.5 per 100,000), Table 1. Since 2012, a decline has been observed in all five Danish regions, but while the incidence in the Capital Region of Denmark, Region Zealand and the Region of South Denmark has roughly been halved in the period, the reductions are only marginal in the Central Denmark Region and the North Denmark Region. In the past five years, the incidence in these latter two regions has remained largely unchanged. From 2021 to 2022, the incidence increase observed at the national level was rooted in four regions, whereas the incidence in the Zealand Region continued to decline, Table 1 and Figure 2.

Origin and country of infection

The expression “of non-Danish origin” comprises immigrants and second-generation immigrants.

Among the 232 notified cases, 59 (25%) were individuals of Danish origin: 40 men and 19 women. For individuals of Danish origin, the median age was 59 years, range 16-91 years.

A total of 173 (75%) cases were notified among individuals of non-Danish origin; 114 men and 59 women. For individuals of non-Danish origin, the median age was 42 years, range 0-87 years.

Figure 3 shows the age distribution of TB cases in 2022, by origin. Among TB cases in individuals of non-Danish origin, the highest number of cases was observed in the 30-59 years age group; and among TB cases in individuals of Danish origin, the highest number was seen in the 60-69 years age group. This trend remains unchanged from previous years.

Figure 4 presents the TB incidence in Denmark by countries recording the highest TB incidences. As previously, the incidence was highest among individuals from Greenland (280 per 100,000 in 2022) and Eritrea (138 per 100,000 in 2022). The incidence of tuberculosis among individuals from high-incidence countries has remained stable for the past years, but has, however, increased slightly from 2021 to 2022 among individuals of Pakistani and Romanian origin.

Presumed country of infection

Based on the notifications, 96 (41%) of the cases were presumed to be infected in Denmark, and 122 (53%) abroad. For 14 cases, the country of infection was unknown. The distribution between those infected in Denmark and abroad has remained unchanged over the past ten years, as shown in Figure 5

TB localisation

Pulmonary TB remains the most frequently notified presentation among individuals of Danish and non-Danish origin alike. However, for individuals of non-Danish origin, the share of extra-pulmonary TB was higher, as previously observed (29% versus 10% for individuals of Danish origin), whereas TB of the lymph nodes was the most frequently occurring type (14%). TB of the central nervous system, a very serious form of TB, occurred only in a very limited number of cases (a total of three cases), Table 2.

Recurrence

A total of 18 patients (8%) were notified with recurrence. This figure remained largely unchanged from previous years when 7% (2021) and 6% (2020) of the cases were recurrences.

TB and HIV infection

Among those notified with TB in 2022, six individuals were HIV positive. In all, among the 232 TB cases notified, 164 individuals had tested HIV negative, whereas the HIV status of the remaining 62 individuals was not provided on the notifications. It remains unknown if these individuals were tested for HIV in connection with their TB diagnosis, or if the cause of the high share with unknown HIV status is that the results of the HIV test were unavailable at the time of the notification.

Tuberculosis among children

In 2022, eight children and young people below 18 years of age were notified with TB. The majority was born in Denmark by parents of non-Danish origin. All of the children had probably become infected in Denmark, and seven of the eight had become infected by a member of the household or a close relative. In one case, the infection source was unknown, and no knowledge was provided about TB infection in the family or social circles. All children diagnosed with TB in 2022 had pulmonary TB. Since 2013, a continued TB decline has occurred among children and young people (33 cases in 2013). This decline is relatively higher than the decline in the total number of TB cases (359 cases in 2013 compared with 233 in 2022), Figure 6.

Tuberculosis among immigrants from Ukraine

In 2022, a total of three TB cases were notified among migrants from Ukraine. One of the three individuals was diagnosed with MDR-TB (multiple resistant TB) in Ukraine and had initiated relevant treatment before arriving to Denmark. The two other cases had isolates that were fully susceptible to second-choice medications. From 2011 to 2021, five cases were notified among migrants from Ukraine; 0-1 case annually.

Occupational transmission

In three cases, it was indicated that the individual had presumably become infected while working. In 2021, the corresponding figure was six.

Microbiological trends

In 2022, only 71% of the individuals of Danish origin who had been notified with TB were confirmed microbiologically. Ideally, approx. 80% of all TB cases should be confirmed to avoid over- or under-diagnosing new cases. Furthermore, microbiological verification ensures species and resistance determination and genotyping for infection tracing purposes.

The number of Danes with a microscopy-positive pulmonary TB, i.e. infectious pulmonary TB, has declined slightly since 2021, from 69% to 65%. This figure, however, remains far higher than the 2020 level, and considerably higher than the 42% recorded in 2019 before the COVID-19 pandemic. Delayed diagnostics generally leads to more serious disease for the individual TB patient, which is reflected in the high share of microscopy-positive patients.

Among those notified for the first time, isoniazid mono-resistance was detected in six (4%) patients, along with a single case of rifampicin mono-resistance. 2022 saw seven cases of multi-drug resistant TB (MDR TB). Additionally, the SSI has knowledge of another five MDR-TB cases that were diagnosed abroad and in which treatment was initiated before the patients arrived to Denmark. TB cases diagnosed abroad are not notifiable in Denmark.

Typing of bacteria from 175 of the 176 (99%) culture-positive patients detected in 2022 shows that a single chain of infection,”C2/1112-15” (also known as Cluster 2), still dominates, accounting for 15% of all typed cases in Denmark. A second infectious chain is nearly as prevalent: C1/1180-213 (Cluster 1), which accounts for 14% of all typed cases. These active infectious chains indicate that active transmission occurs in Denmark, typically among vulnerable/marginalised individuals.

This report is also described in EPI-NEWS no. 51b/2023.