Malaria 2017

Annual report on imported malaria 2017

In 2017, a total of 94 cases of imported malaria were detected by Danish laboratories, Table 1.

Information about presumed country of infection was retrieved for all 94 cases. The majority of the patients had become infected during stays in Africa, 88% (83/94). Cases were roughly equally distributed geographically between countries situated in West Africa, East Africa and in Central and South Africa. Even so, a strikingly high number of cases were associated with a single country;

The Ivory Coast in West Africa, where 12 persons became infected with malaria, 11 of whom were of non-Danish origin. A total of 11% (10/94) of this year’s malaria cases had become infected in Asia; all cases were from Afghanistan, Pakistan or India. Thus, as previously, 2017 saw no cases of imported malaria among travellers to South-East Asia. In a single malaria case, infection occurred in Central America (either Costa Rica or The Dominican Republic), which is considered a low-risk area. No cases were reported from Oceania.

Overall, 71% (67/94) were caused by Plasmodium falciparum, 17% (16/94) by Plasmodium vivax and 9% (8/94) by Plasmodium ovale, whereas 1% of the cases were due to Plasmodium malariae (1/94). Nearly all falciparum malaria cases had become infected in Africa, 99% (66/67). In contrast, no falciparum cases were observed among travellers returning from Asia, whereas the only case imported from Central America was due to P. falciparum. Among the cases from Africa, 80% (66/83) were caused by falciparum malaria, whereas 10% (8/83) were due to P. ovale. A total of 7% (6/83) of the malaria cases from Africa were caused by P. vivax, all of which occurred in travellers from Eritrea/Ethiopia, as was also the case for the past three years, EPI-NEWS 25/15, 26/16 and 26/17. All malaria cases imported from Asia were caused by vivax malaria.

Several patients had relapse of vivax malaria within months after the primary diagnosed episode, but these extra episodes were recorded as part of the primary infection and therefore do not form part of the annual report on malaria cases.

The overall median age for the reported malaria cases was 37 years (range 2 to 78 years). A total of ten cases were children below 10 years of age, all of whom formed part of families of non-Danish origin. 62% (58/94) of the cases occurred in male travellers, 38% (37/94) in female travelers. Overall, nearly 3/4 of the travelers who returned with malaria (or their parents) were of non-Danish origin.

Figure 1 presents the development in the number malaria cases imported to Denmark since 1998, by place of infection, whereas Figure 2 presents the development in the number of cases by type of malaria detected in Denmark since 1998.

Improvement of the ongoing national malaria monitoring through use of The Danish Microbiology Database, the MiBa

For the first time ever, the annual malaria report is based, in part, on a supplemental data extraction from The Danish Microbiology Database (The MiBa). This was done to track additional malaria cases that were diagnosed at one of the Danish departments of microbiology, but which had not been notified despite the laboratories’ duty to notify in pursuance of the current executive order on notification of infectious diseases. Thus, only 44 cases had been notified for all of 2017 when a count was performed in March 2018. Some laboratories had reported only some cases to Statens Serum Institut (SSI), others had not reported any cases at all. Following the SSI’s contact to the departments of microbiology, the number of officially reported cases rose to 85. A search in the MiBa using a novel malaria algorithm identified another nine cases that had not been notified. These additional cases form part of the year’s analysis. It is our intention, in collaboration with the departments of microbiology, to perform an additional validation of the novel MiBa malaria algorithm.

This report is described in EPI-NEWS 26/18.