the line listing of ha patients included persons with laboratory evidence of recent hav infection ( anti - hav immunoglobulin m [ igm ] ) who stayed at hotel x after june 1 , 2004 . also listed were hotel guests with ha disease ( jaundice , elevated liver enzyme levels ) , without laboratory confirmation , who had traveled with persons with laboratory - confirmed cases .
a case - control study was performed among hotel x guests > 17 years of age residing in 3 german states .
the time span between the earliest arriving case - patient 's last day at hotel x and the latest arriving case - patient 's first day there was defined as the " minimum period of transmission " ( mpt ) .
healthy hotel guests who stayed at the hotel during the mpt who had neither been vaccinated against hav nor previously infected with hav were eligible as controls .
telephone interviews were conducted with a standardized questionnaire that elicited information on demographic factors , foods and drink consumption , and participation in recreational activities such as swimming , day trips , etc . for statistical analysis
, exposures were dichotomized into " ever " versus " never , " and the " number of days exposed " was calculated .
univariate analysis (  tests ) and multiple logistic regression were performed ( spss version 12.0.2 , spss inc . , chicago , il , usa ) ;
the egyptian authorities ' investigation included testing all hotel employees for hav antibodies ( igm , igg ) , and scrutiny of food suppliers .
serum samples were obtained from german case - patients for testing by reverse transcription  pcr ( rt - pcr ) in the vp12a junction and sequencing of a 160-bp - long pcr fragment of the vp1 region .
the outbreak lasted from july 10 to september 8 , 2004 ( figure 1 ) .
a total of 351 case - patients made up this outbreak : 271 primary and 7 secondary infections in germany , plus 60 primary infections reported to the national public health institutes in 8 other european countries .
austria recorded a secondary outbreak with 13 cases caused by an infected food handler who had stayed at hotel x ( 3 ) . in preceding years , in germany only 28 ha cases were reported after travel to egypt with disease onset between july 10 and september 8 .
epidemic curve : distribution of dates of disease onset for outbreak - associated hepatitis a case - patients from germany ( n = 264 ) , and minimum period during which hepatitis a virus transmission occurred ( mtp ) . of
the german reported primary cases , overt clinical ha developed in 263 ( 97% ) persons .
case - patients were 2 to 67 years of age ( median 34 years ) and 54% were male .
no more than 52% of the case - patients had stayed together at the hotel on any single day .
case - patients had stayed at hotel x from 6 to 21 days , and 70% had stayed 13 days or longer .
sixty - nine ha case - patients ( 60% response among the 115 case - patients in the 3 states ) and 36 controls were included in the statistical analysis .
eighty - seven percent of the case - patients reported absence from work for 3 to 56 days ( median 26 days ) , and 54% of the case - patients were hospitalized for 2 to 25 days ( median 9 days ) .
case - patients and controls did not differ significantly by age , sex , recreational activities , consumption of ice cream or salads , or other foods consumed or behavioral characteristics .
case - patients were significantly more likely to have drunk orange juice served at the breakfast buffet ( 82% ) than were controls ( 64% ) ( odds ratio 2.6 ; 95% confidence interval 1.16.6 ) .
a dose - response relationship became apparent between number of days of orange juice consumption and ha ( figure 2 ) .
case - patients consumed orange juice for a median of 11 days , and controls consumed it for a median of 5 days . in 22 ( 52% ) of the 42 serum samples available for testing ,
all samples compared by sequencing were identical and belonged to genotype 1b ( figure 3 ) .
days of orange juice consumption among hepatitis a patients and controls . or , odds ratio ; ci , confidence interval .
phylogenetic analysis of the vp12a junction region . the sequence of a 160-bp - long pcr fragment ( isolate egy/1/05/deu , genbank accession no .
ay741663 ) of the hepatitis a vp1 region was compared to published reference sequences of hepatis a virus .
aj306374(arg-1 ) , ay656712 ( bav/2/03/deu * ) , ay028976 ( sa/10/2000/deu ) , ay046073 ( datteln/01/deu ) , and ay747173 ( nrw/3/04/deu * ) . genotype ib : l07728 ( jor 88 ) , m14707 ( hm-175 ) .
the scale represents nucleotide substitutions per position ( * denotes previous german outbreak - causing strains ) .
the on - site investigations in egypt did not identify hotel staff positive for hav igm .
minimal fluctuation among hotel staff renders it unlikely that an hav - positive employee was missed .
this large outbreak demonstrates risk and clinical impact of ha for nonimmune travelers to ha - endemic countries . in germany , the outbreak accounted for 12% of all ha case - patients notified in the year 2004 .
the results of the outbreak investigation strongly point to orange juice as the infection vehicle . in the case - control study , among a broad range of foodstuff , beverages , and recreational activities queried , the consumption of orange juice was the only exposure significantly associated with ha , with higher doses of juice significantly increasing ha risk .
these findings are corroborated by the inspection of the hygienic conditions under which the juice was produced in egypt .
the juice was most likely contaminated during the manufacturing process , e.g. , by an infected worker with imperfect hand hygiene or by contact of fruit or machinery with sewage - contaminated water .
citrus fruit and citrus juices have only rarely been implicated as vehicles of ha outbreaks , with contamination typically described during preparation just before consumption ( 4,5 ) .
salmonella outbreaks caused by orange juice contaminated at the production site have been identified ( 68 ) .
as hav is quite resistant to acid ( 9 ) , it likely survives for prolonged periods in orange juice .
less stable pathogens such as escherichia coli have been shown to survive in orange juice for > 15 days ( 10 ) .
the fact that juice was consumed by 60% of healthy controls may be explained in part by fluctuating virus concentration within the juice , which resulted in varying degrees of infectiousness during the 4-week period .
a contaminated lot may have been phased - in and out slowly by gradual mixture with other lots .
also , the study design did not allow the exclusion of controls who did not know they were immune .
the hurghada outbreak - strain clearly differs from strains that have caused nontravel - associated outbreaks in germany in recent years .
two large autochthonous outbreaks were caused by hav type 1a strains ( 11 ) . in the netherlands , hav strains in autochthonous cases
mostly also belonged to hav 1a , whereas 1b strains were found more often in children of moroccan origin ( 12 ) .
extended monitoring of hav strains , for example , as performed in the united states ( 13 ) , could find hidden clusters and demonstrate links between imported and autochthonous cases .
vaccination against ha is recommended for all nonimmune travelers to ha - endemic areas ( 14 ) .
this outbreak showed that a high proportion of german tourists in egypt were either not adequately informed about ha risk and the benefits of vaccination or were informed yet still decided against vaccination .
the outbreak emphasizes the importance of adequate pretravel advice , preferably from an institution specialized in travel medicine .
 in 2004 , a major outbreak of hepatitis a among tourists returning from egypt involved 351 case - patients from 9 european countries who were infected with a single strain ( genotype 1b ) . 
 the case - control study identified orange juice as the most likely infection vehicle . 
 vaccination against hepatitis a virus is strongly recommended before travel to disease - endemic areas . 
The Study
Conclusions