No 51b - 2023

Tuberculosis in 2022

In 2022, Denmark saw a total of 232 notified cases of tuberculosis (TB).

For a detailed epidemiological description of the 2022 occurrence, please see the 2022 Annual Report on TB Incidence

In 2022, the total incidence of TB in Denmark was 3.9 cases per 100,000 inhabitants. As in the preceding years, the highest incidence was seen in the Capital Region of Denmark (4.8 cases per 100,000); and within that region, the highest incidence was recorded in the City of Copenhagen area (6.6 per 100,000) compared with the remaining regions and areas.

Incidence trends

In the 2020-2022 period, the incidence 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 was probably associated with a lull in the number of tests and clinical notifications compared with the period leading up to the COVID-19 pandemic, Figure 1.

For the decade leading up to 2020, a decline in incidence was registered in all regions, but more so in the Capital region of Denmark, the Zealand Region and the Region of South Denmark, where the incidence has nearly halved since 2013. Opposite this, the decline observed in the Central Denmark Region and the North Denmark Region was very limited. From 2021 to 2022, the incidence increase observed at the national level occurred in four regions, whereas the incidence in the Zealand Region continued to decline.

Case median age

The median age for TB cases of Danish origin was 58 years, which is an increase from the 51 years recorded in 2021. For individuals of non-Danish origin, the median age was 42 years, which is unchanged from previous years. Thus, the age profile among TB cases in the two groups is very different and the highest incidence among individuals of Danish origin was seen in the 60-69-year age group, whereas the highest incidence among individuals of non-Danish origin was seen in the 30-59-year age group. This difference has remained unchanged for the past decade.

Presumed country of infection

Based on notifications, 96 (41%) of the cases were presumed infected in Denmark and 122 (53%) abroad. For a total of 6%, the country of infection was unknown. Overall, the number suggest an unchanged distribution between those infected in Denmark and abroad over the past 10 years. The fact that 41% are infected in Denmark overall, and that this proportion has remained constant over the past 10 years, indicates that there is still a significant need to detect and break transmission chains in Denmark.

Type of tuberculosis

Pulmonary TB remains the most frequently notified presentation among individuals of Danish and non-Danish origin alike, where the shares were 90% and 71%, respectively. TB of the central nervous system, a very serious form of TB, only occurred in a very limited number of cases (a total of three cases).

Microscopy positivity

The share of individuals with microscopy-positive pulmonary TB, where TB bacteria are observed by microscopy of expectorate, declined slightly in 2022 compared with 2021. However, the number of cases recorded in 2022 remains higher than before the COVID-19 epidemic. Microscopy positivity indicates infectiousness and also provides information about how late the condition was detected as a late diagnosis increases the risk of microscopy positivity. It remains unclear exactly what caused the increase in microscopy positivity. However, during the COVID-19 pandemic, screening activities in the risk environments were low, at least in the Copenhagen area. This may have contributed to the increase along with reduced access to diagnostics during the COVID-19-related restrictions.

Tuberculosis among children

A total of eight children below 18 years of age were notified with TB in 2022 (14 cases in 2020, 11 cases in 2021). All of the children were presumed to have been infected in Denmark, and seven of the eight had become infected by a member of the household or a close relative, whereas the source of infection was unknown for one child. All had pulmonary TB. Despite the low and decreasing number, it signifies that the children are getting infected in Denmark by a household or close family member, emphasizing the ongoing need for special attention to children among the contact of TB cases.

HIV among TB cases

Among the 232 individuals notified with TB in 2022, six individuals were HIV-positive. Among the six HIV-positive cases, two were newly diagnosed, and four were known to be HIV-positive. A total of 164 individuals were HIV-negative. For the remaining 62 individuals, the HIV status was unknown or undisclosed. As HIV is a significant risk factor for TB disease, it is crucial to test for HIV concurrently with TB diagnosis unless the patient is already known to be HIV-positive.

Tuberculosis among immigrants from Ukraine

There has been a significant international attention on TB cases among migrants from Ukraine. In 2022, three cases of TB were notified among migrants from Ukraine. One of the three had been diagnosed with MDR-TB in Ukraine before arriving in Denmark, was already three months into the anti-tuberculous treatment, and had no pulmonary symptoms, resulting in a very low risk of further transmission in Denmark.

From 2011 to 2021, a total of five cases were notified among migrants from Ukraine; ranging from zero to one case per year.

Thus, an increase has, indeed, been observed, but a modest and expected one given the increased number of migrants from the Ukraine in 2022.

Generally, special attention is required to TB risk factors among migrants from the Ukraine and from other mid- and high-incidence countries. This applies to asylum centres but also to general practice where migrants are seen who have not previously been housed at an asylum centre. Tuberculosis should therefore be considered in case of:

1. Symptoms consistent with TB, mainly coughing, blood-stained sputum, fever, weight loss and/or night sweats or
2. close contact to an individual who has become infected with tuberculosis or
3. previously known to have tuberculosis.

Summary

For the years 2020-2022, the incidence of TB has remained relatively 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 was likely associated with fewer tests and clinical notifications than before the COVID-19 pandemic. There have been no significant changes in the general distribution of TB cases concerning gender, age, origin, and type of TB (pulmonary versus extrapulmonary TB).

Based on notifications until the end of November 2023, only 130 cases have been notified in Denmark, which corresponds to 60% of the notifications at the same time in 2022. While acknowledging the possibility of delayed notifications, this decline is more significant than in previous years. However, in 2022, paper-based notification of infectious diseases was replaced by electronic notification, and we cannot exclude that this may have affected the number of TB notifications made based on clinical criteria alone. All microbiologically verified TB cases are detected via the Department of TB and mycobacteria at Statens Serum Institut. Therefore, it is possible to send out reminders for any lacking notifications.

Although the occurrence of TB follows a declining trend, it is essential to remain attentive to TB in Denmark, focusing on diagnosis, contact tracing, prevention and notification of the disease – especially in cases diagnosed based solely on clinical criteria.

(L.H. Holm, A. Koch, Department of Infectious Disease Epidemiology and Prevention, T. Lillebæk, D.B. Folkvardsen, Department of Tuberculosis and Mycobacteria)