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Home Eurosurveillance Weekly Release  2004: Volume 8/ Issue 26 Article 2
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Eurosurveillance, Volume 8, Issue 26, 24 June 2004

Citation style for this article: Wichmann O, Mühlberger N, Jelinek T. TropNetEurop surveillance data: Trends in imported malaria 2003. Euro Surveill. 2004;8(26):pii=2492. Available online:

TropNetEurop surveillance data: Trends in imported malaria 2003

Ole Wichmann (, Nikolai Mühlberger, and Tomas Jelinek, Berlin Institute of Tropical Medicine, Germany, for the European Network on Surveillance of Imported Infectious Diseases (TropNetEurop,

Falciparum malaria remains one of the most important killers worldwide and the most frequent cause of travel related fever in European travel clinics. Since its foundation in 1999, the European Network on Imported Infectious Disease Surveillance (TropNetEurop, has been targeting imported malaria [1, 2]. The network currently consists of 46 collaborating centres in 15 European countries and produces reports for its members on a monthly basis. The 2003 data on imported falciparum and tertian (Plasmodium vivax and P. ovale) malaria are presented in this report.

Overall, 831 cases of falciparum malaria were reported to the network’s coordination centre in 2003 (818 mono- and 13 mixed infections) and 145 cases of tertian malaria: 113 infections with P. vivax and 32 with P. ovale.

Falciparum malaria
When comparing 2003 data with data from 2002, patient characteristics appear to remain unchanged despite the steady growth of TropNetEurop and the addition of new reporting centres across the continent. The majority of patients were male (65%) with a median age of 36 years and a median travel duration of 30 days. Patterns of geographic distribution where cases were acquired were similar in 2002 and 2003, although South East Asia was less frequently reported as an area where the malaria was acquired. West Africa continues to be the most common source of infection, with Nigeria, Cameroon and Ghana heading the list in 2003 (Figure 1).

Figure 1. Countries contributing large numbers of falciparum malaria patients to Europe in 2003. n=812. Source: TropMedEurop.

The majority of travellers with falciparum malaria (75%) did not use any chemoprophylaxis during their trip abroad. However, 5.7% of patients used mefloquine for chemoprophylaxis, and 6.4% used chloroquine and paludrine. Doxycycline was used by 1.7% and proguanil/atovaquone by 0.7% of the travellers. These data do not give information about actual prophylactic failures since compliance is difficult to assess.

When comparing 2003 data with 2002 data, the proportion of cases in foreign born persons living in Europe has increased from 49% to 55%. The main reason these patients gave for travelling was visiting friends and relatives in their malarious home countries. This finding poses a challenge to European healthcare systems since many in this group may be unaware that they need protection and malaria chemoprophylaxis (especially when they have been away from the endemic area for several years). A large and increasing group of patients of European origin are business travellers (almost 19%). It would appear that their pre-travel advice and preparation are not adequate.

The majority of patients became symptomatic within a very brief period after their return to Europe (median of 4 days) and did not wait long to seek medical care (median 4 days). The distribution of symptoms in 2003 is nearly the same as in 2002 although the incidence of diarrhoea has increased (Figure 2). Ninety two percent of patients with falciparum malaria presented with fever. A large proportion had gastrointestinal symptoms. Vomiting was reported in 18% and diarrhoea in 16%. These gastrointestinal symptoms may interfere with absorption of oral antimalarial therapy.

Figure 2. Distribution of reported symptoms in 728 patients with falciparum malaria imported to Europe in 2003. n=728. Source: TropNetEurop.

Although guidelines in most European countries recommend treating patients with falciparum malaria on an inpatient basis, the proportion of patients being treated as outpatients is steadily increasing. For those who stayed in hospital, the median length was 4 days with a maximum of 90 days in complicated cases. This is a decrease from 2001, when the median stay was 5 days with a maximum of 100 days. However, this difference was not statistically significant (P=0.38). The rate of cerebral malaria has slightly increased in comparison with 2002 from 0.7% to 1.1% and the rate of other complications from 5% to 5.7%. The overall case fatality rate in 2003 (n=7 or 0.9%) is slightly lower than in 2002 or 2001. The case fatality rate in patients with complications in 2003 (n=50) was slightly higher than in 2002 (14% versus 12.5%, respectively).

Quinine remains the most commonly used antimalarial drug for treatment in Europe (Table). Atovaquone/proguanil is the second most often used drug (15.8%). Mefloquine has seen a recovery in use for treatment (13.3%) rates in comparison to 2002. If compared to 2002, artemether/lumefantrine has increased its share from 2.3% to 3.2%.

Table. Drugs used in the treatment of imported falciparum malaria in European in 2003 (multiple entries possible). Source: TropMedEurop.


Drugs Number % Cumulative Cumulative
      number %


Tertian malaria
Similar to previous years, patients with tertian malaria (P. vivax and P. ovale) tended to be male (61%) with a median age of 33 years, travelling with a median time of 53 days abroad. Many patients who developed tertian malaria did so despite chemoprophylaxis. This is not surprising since the commonly used prophylactic drugs apart from primaquine cannot be relied upon to prevent the development of hypnozoites of P. vivax and P. ovale in the liver. A total of 17.8% of tertian malaria patients took mefloquine for prophylaxis while travelling abroad, 11.5% took chloroquine alone or in combination with proguanil, 4% took doxycycline, 2.9% took atovaquone-proguanil and 0.6% took proguanil alone (53% took no prophylaxis at all and for 10.3% no data were available).

Unlike in falciparum malaria, the proportion of European-born patients with tertian malaria remains high (67%). The majority of these patients were travelling as tourists. Missionary work was the second most common reason for travel, followed by business. The geographical distribution of tertian malaria continues to be more varied than in falciparum malaria. High proportions of travel acquired infections imported into Europe are in travellers returning from Pakistan, Indonesia, India and Papua New Guinea (Figure 3).

Figure 3. Countries contributing to tertian malaria importation into Europe in 2003. n=151. Source: TropMedEurop.

As recently published [3, 4], the majority of patients with tertian malaria became symptomatic after a rather extended period of time following their return to Europe with a median of 65 days. A delayed onset might be caused either by a prolonged primary latency or if the appearance of the infection is suppressed by partially effective chemoprophylaxis. Unlike in falciparum malaria, atypical symptoms were rare in tertian malaria. Besides fever, 55% of patients presented with headache, 35% with fatigue and 27% with musculoskeletal pain. In 14% of cases, patients suffered from vomiting and in 10.4% from diarrhoea. Complications were reported in 11 (7.6%) of the patients. These included relapses (n=5), severe thrombocytopenia, anaemia, and abnormal liver function tests. No deaths are reported.

As in 2001 and 2002, many patients were admitted to hospital (62.1%), and the median hospital stay was not much shorter than for falciparum malaria (3 days versus 4 days, respectively). On average, 27.7% of all patients with tertian malaria did not receive primaquine for relapse prophylaxis following treatment.

  1. Jelinek T, Schulte C, Behrens R, Grobusch MP, Coulaud JP, Bisoffi Z, et al. Imported Falciparum malaria in Europe: sentinel surveillance data from the European network on surveillance of imported infectious diseases. Clin Infect Dis 2002; 34:572-6. ( [accessed 23 June 2004]
  2. Jelinek T, Peyerl-Hoffmann G, Muhlberger N, Wichmann O, Wilhelm M, Schmider N, et al. Molecular surveillance of drug resistance through imported isolates of Plasmodium falciparum in Europe. Malar J 2002; 1:11. ( [accessed 23 June 2004]
  3. Schwartz E, Parise M, Kozarsky P, Cetron M. Delayed onset of malaria--implications for chemoprophylaxis in travelers. N Engl J Med 2003; 349:1510-6.
  4. Muhlberger N, Jelinek T, Gascon J, Probst M, Zoller T, Schunk M, et al. Epidemiology and clinical features of vivax malaria imported to Europe: sentinel surveillance data from TropNetEurop. Malar J 2004; 8:5. ( [accessed 23 June 2004]

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