Danish health authorities reported 94 imported malaria cases in 2017, a number roughly on a par with the level recorded in the past few years–about 100 cases per year.

Mature Plasmodium vivax schizont/CDC
Mature Plasmodium vivax schizont/CDC

Compared with 2014, 2015 and 2016, the year 2017 recorded a lower occurrence of vivax malaria among refugees arriving to Denmark from Eritrea/Ethiopia. The same trend has been observed in other Northern European countries.

However, they warn there is still a need to be attentive to vivax malaria in persons from Eritrea, particularly in children. In some cases, vivax malaria presents as a mild subclinical infection, which may even not present until several months after a stay in a risk area.

It is conceivable that some of the patients who have arrived from Eritrea may already have received malaria treatment previously in their disease course in the form of a schizonticidal drug (e.g., artemether/lumefantrine or atovaquon/proguanil). They have therefore recovered temporarily, but vivax malaria recurs in these patients due to lacking radical treatment with primaquine, as was observed in several cases in Denmark in the course of 2017.

In contrast to the decline in vivax malaria cases among Eritrean refugees, 2017 has recorded a slight increase in the number of malaria cases from Africa caused by Plasmodium falciparum and Plasmodium ovale.

The 2017 figures thus confirm that for common travellers, the risk of malaria is mainly the risk of serious falciparum malaria in Africa, whereas the risk of malaria outside of Africa is very limited and mainly due to vivax malaria. Immigrants and their children who visit their countries of origin generally constitute the main risk group, as these persons typically stay for longer periods of time with their families, sometimes in areas with a considerable local risk of malaria.

As in previous years, 2017 recorded a relatively high number of malaria cases from the following three countries: Afghanistan, Pakistan and India. In contrast, no malaria cases were seen among travellers returning from the remaining parts of Asia, including the majority of South-east Asia, despite the large number of Danish tourist travellers to several of these countries. Furthermore, only a single case of malaria was observed in a traveller returning from Central America, where the risk of becoming infected with malaria as a traveller should therefore be considered low.