fever in returning travelers is a common problem and usually the diagnosis is made within a few days or the traveler recovers , . we report here two travelers who presented with fever two weeks after returning from a six week vacation in south america . over the following 18 months they presented with short attacks of fever , elevated crp and leukocytosis and a curious and key feature was , that they were completely synchronous both developing symptoms within an hour and presentation with the same laboratory findings of leukocytosis and elevated crp . after about a year it turned out that the couple used aroma oils ( nature and decouvertes  fig . 1 ) in the home applied by a nebulizer placed in the middle of a table . the oils were not used during summer , also explaining the absence of symptoms during the summer months . since the use of the oils ended there has been no relapse in any symptoms . we are not aware of or have found any previous reports , in english or other languages , reporting similar events after the use of similar products . after traveling to south america for a six weeks tourist holiday the two patients returned home to denmark . ten days after returning they were both admitted to hospital with fever , muscle and joint pains and vomiting . from the 8 september 2012 to the 22 october 2012 they spent 3 weeks in peru , half a week in bolivia , half a week in chile and 2 weeks in brazil . they traveled by local busses , stayed at medium level hotels and were not ill at any time during their travels . prior to their travels they had received vaccines against hepatitis a and b , yellow fever and tetanus / diphtheria . table 1 shows the patients history and table 2 lists crp , white blood cell count and recorded rectal temperatures . day 0 is defined as the first day the couple was admitted to hospital , 10 days after the return from south america . there was no eosinophilia at any given time and the total ige remained normal throughout . approximately nine episodes occurred within the following 18 months , all attacks being identical in symptoms , duration and paraclinical results for both patients ( table 2 ) . initially the patients were tested negative for malaria and dengue fever . under the suspicion of a rickettsial infection they were treated with doxycycline 100  mg two times daily initially for one week . this was immediately afterwards repeated again for one week . after the third relapse , day 20 , the patients received 3 months doxycycline 100  mg two times daily plus moxifloxacin 400  mg    1 , as it was believed they previously had had a good effect . the patients went through an elaborate program of serological tests and test for nucleic acids of different pathogens , which is summarized in table 3 . through the whole course a wide range of tests were performed including heart echocardiography , pet - ct and an mri which were all normal . definition of travel associated disease  is a patient who has crossed an international boarder within the past 10 years and presents for a presumed travel - related disease  . it is not uncommon for travelers to report an illness associated with their travels ( 2070% ) , but only a small portion of these actually seek medical attention , , . a detailed medical history is a very important tool in correct diagnosis , including destinations , risk factors , previous medical history . incubation time is also important to keep in mind through the process ( table 5 ) , , . the geosentinel surveillance program has found that the most common causes of fever after traveling is malaria , dengue fever , enteric fever ( salmonella typhi ) and rickettsioses . initially malaria and dengue fever were excluded and the patients were treated with doxycycline under the presumption of a rickettsia or bartonella infection . when the fever attacks continued we excluded endocarditis due to coxiella burnetii ( q fever ) and looked for south american trypanosomiasis due to trypanosoma cruzi ( chagas disease ) , which can be transmitted orally through fresh fruit juice . we speculated that toxoplasma gondii was a possibility as t. gondii genotypes in south america are more pathogenic compared to europe , but only one of the subjects had antibodies at a low titer , not compatible with an acute infection . leptospirosis was also a diagnostic option , especially with a second phase of fever shortly after the first ; this was however also excluded by a negative serology . acute schistosomiasis and other parasites were ruled out as there was no eosinophilia or elevated total - ige in either patient . different centers were asked to assist with this case , including unit des rickettsies , france , porton down , uk and center for disease control and prevention ( cdc ) , united states . see table 3 , table 4 for list of all the test and results found on the patients . cytomegalovirus and epstein  barr virus were also considered as they are a common cause to fever of unknown origin in adults . hiv and other sexually transmitted diseases were also screened for and these results were also negative . the patients were not tested for histoplasmosis as this rarely causes a prolonged course of disease in immunocompetent patients . throughout the long period of symptoms with this couple it became more and more apparent that it was not an infectious agent at play . the attacks were short lived and the crp and leukocytosis normalized within a few days . malignancy and inflammatory diseases were also ruled out as the cause of the recurrent fever . both patients had a slight dry cough and small , non - tender , lymph glands at several stations . one would expect the patients to react differently to the same infectious agent as their immune systems are different as they differ genetically . we , therefore , started searching for an agent they could both be exposed to in the home . all the symptoms seemed to occur during autumn , winter and spring  during which the windows are closed . it is therefore believed to be repeated exposure to aroma oils ( nature and decouvertes ) that is the cause of the symptoms . since the exposure has stopped there have been no more events . for ethical reasons it has not been possible to test with expose . the oils used here were nebulized and we assume that the two patients inhaled a high concentration of the nebulized oils over a short time . this was actually recommended by the manufacturer and the oils and table top nebulizer was purchased together . as mentioned earlier , we are not aware of reports of any similar events after using other similar products . the investigational program was build up over time as new attacks continued to occur and suggestions from different centers which were consulted were followed up . the number of tests performed at different laboratories took time and emphasizes that a panel of analysis in returning travelers with continued symptoms but without a clear diagnosis should be developed . written informed consent was obtained from the patient for publication of this case report and accompanying images . a copy of the written consent is available for review by the editor - in - chief of this journal on request .
fever in returning travelers is a common problem and usually the diagnosis is made within a few days or the traveler recovers.we present two travelers who presented with fever two weeks after returning from a six week vacation in south america . over the following 18 months they presented with short attacks of fever , elevated crp and leukocytosis and 
 the program for investigation became more and more elaborate . 
 a curious and key feature was , that they were completely synchronous both developing symptoms within an hour and presentation with the same laboratory findings of leukocytosis and elevated crp . 
 extensive and repeated tests were performed , at our facility and abroad . after a year 
 it was discovered that the uses of aroma oils were associated with the symptoms . 
 no similar case has been found to be reported previously.these cases emphasize that natural products are not inherently safe . 
 the investigational program was build up over time as new attacks continued to occur and suggestions from different centers which were consulted were followed up . 
 the number of tests performed at different laboratories took an extensive amount of time . 
 these cases emphasize that a panel of analysis in returning travelers in which no clear diagnosis is found should be developed .