in may 2001 , 24 cases of s. typhimurium dt160 salmonellosis were reported in the auckland region compared with an average of four sporadic cases each month with this serotype in the previous 7 months .
raw and undercooked egg consumption was commonly reported by the first 10 case - patients interviewed .
a case - control study and environmental investigation were undertaken to identify the vehicle of infection and source of the outbreak .
recognizing the potential for a widely dispersed foodborne outbreak , we expanded the investigation throughout new zealand .
we defined a case as diarrhea ( 3 loose stools in a 24-hour period ) or vomiting after april 28 , 2001 , with a stool specimen positive for s. typhimurium dt160 .
patients were excluded if they had a history of contact with another person with culture - confirmed s. typhimurium dt160 infection , or if they had a history of recent overseas travel . each case
was matched with two controls found from randomly drawn telephone numbers , matching for neighborhood and age ( < 1 , 14 , 514 , > 14 years ) .
the questionnaire covered symptoms ( patients only ) and contact with other symptomatic persons , bird or animal contact , and food consumption in the 3-day period before onset of illness ( cases and controls ) . parents or guardians were interviewed on behalf of children ages < 12 years .
stepwise conditional logistic regression analyses were performed , also using sas , to identify the combination of variables that best explained the differences between case - participants and controls .
samples from the drinking water supply of case - patients with a history of recent consumption of nonreticulated water were collected and tested for coliforms and s. enterica by using standard methods ( 6 ) .
brands of eggs eaten raw within the incubation period were sampled at random from retail displays at the case - patients purchase site .
eggshell surfaces and contents were tested with standard methods ( 7 ) . broken or cracked eggs were excluded from analysis .
salmonella isolates were serotyped by using the kauffman - white scheme ( 8) and s. typhimurium isolates were phage typed by using the laboratory of enteric pathogens method ( 9 ) . from may
to august 2001 , a total of 170 case - patients meeting the case definition were identified . of these , 119 ( 70% )
agreed to participate and were enrolled in the study , along with 235 matched controls .
the median age of case - patients was 8 years ( range 4 months to 90 years ) , and 57% were female .
the most frequently reported symptoms were diarrhea ( 97% ) , abdominal pain ( 77% ) , excessive tiredness ( 67% ) , and fever ( 66% ) .
the median duration of illness was 7 days ( range 144 days ) ; 17 ( 15% ) patients were hospitalized , and none died .
case - patients and controls did not differ significantly according to age , sex , immunosuppressive therapy , treatment to reduce gastric acidity , or use of antibiotics .
all s. typhimurium dt160 isolates were sensitive to ampicillin , cephalothin , chloramphenicol , ciprofloxacin , co - trimoxazole , gentamicin , streptomycin , sulfonamides , tetracycline , and trimethoprim .
four represented different levels of contact with other persons with gastrointestinal illness ( i.e. , within 28 days of illness onset ; within 3 days of onset ; within the household ; or outside the household ) . direct handling of dead wild birds , consumption of fast food , and consumption of food at a large gathering , such as at a party or large barbecue , were also significantly associated with illness .
after stepwise regression , contact with a person with gastrointestinal illness in the 28 days before onset of illness in the case - patient ( adjusted odds ratio [ or ] 2.8 ; 95% confidence interval [ ci ] 1.4 to 5.4 ) , exposure to dead wild birds ( adjusted or 10.5 ; 95% ci 2.3 to 47.5 ) , and consumption of fast food ( adjusted or 1.7 ; 95% ci 1.0 to 2.9 ) had independent significant associations with illness .
dt , definitive type ; d&v , diarrhea and vomiting ; or , odds ratio ; ci , confidence interval .
twelve case - patients throughout new zealand indicated that they had drunk water from nonreticulated and untreated water sources .
seven patients used roof - collected rainwater , and one used rainwater plus water from a dam .
four of the five patients who had eaten raw eggs could identify the retail brand and outlet of purchase .
these four patients had purchased six different brands of eggs from seven different retail outlets .
samples for two brands were positive for s. thompson , both from shell surface washings .
epidemiologic investigation of an outbreak of s. typhimurium dt160 infection in new from may to august 2001 found that contact with dead wild birds , contact with other persons with gastrointestinal illness , and consumption of fast food were all significantly associated with illness .
in addition , s. typhimurium dt160 was found in roof - collected rainwater drunk by five patients .
s. typhimurium dt160 had been previously identified as the cause of large numbers of sparrow deaths in new zealand in 2000 , and analysis by pulsed - field gel electrophoresis ( using the method described by barrett et al
.   and restriction enzyme xbai ) demonstrated that bird and human isolates in 2000 were indistinguishable ( 4 ) . in our study , information was not collected on exposure to environments contaminated by wild bird feces , such as parks and play areas , a fact that may have underestimated the avian contribution to human illness .
s. typhimurium dt160 has previously been recognized as a bird pathogen in canada ( 11 ) and in england ( 12 ) . before its emergence in new zealand , the human s. typhimurium
dt160 infection had only been reported in the context of a 1979 institutional outbreak in the united kingdom , linked to food contamination by sparrow droppings ( 13 ) .
consumption of undisinfected water has previously been identified as a risk factor for salmonellosis linked to bird transmission ( 14 ) .
this risk factor was not confirmed by our case - control study , despite the finding of s. typhimurium dt160 in roof - collected rainwater .
this discrepancy is probably because case - patients and controls were matched by neighborhood , and types of water sources are usually consistent within neighborhoods .
the association of illness with contact with another person with gastrointestinal illness is likely underestimated because secondary salmonellosis cases were excluded .
consumption of fast food was associated with illness ; however , no single type of food outlet or food was identified .
case - patients were equally likely to have eaten food from chain fast - food restaurants as from family - owned fast - food outlets .
consumption of fast food may have occurred in environments contaminated by bird feces , or the foods themselves may have been contaminated , either during production or by infected foodhandlers ( 15 ) .
asymptomatic salmonella carriers would not have been excluded from selection as controls , potentially reducing the magnitude of observed associations .
recall may have been influenced by delays between exposure and interview , although participants were asked to refer to a memory aid ( personal diary or calendar ) .
the investigation successfully excluded a single common source exposure for this outbreak and instead suggested that multiple exposures contribute to s. typhimurium dt160 infections in new zealand .
strategies for addressing these exposures include routine treatment of roof - collected rainwater , hygienic disposal of dead birds , and promotion of hand - hygiene protocols and sick foodhandler policies in fast - food outlets .
the source of this incursion of s. typhimurium dt160 into new zealand remains unknown : bird isolates have been exclusively from nonmigratory birds , s. typhimurium dt160 has not been identified in neighboring countries in the pacific basin , and early case - patients did not have a history of overseas travel .
 an outbreak of human salmonella enterica serotype typhimurium dt160 infection in new zealand was investigated from may to august 2001 . 
 handling of dead wild birds , contact with persons with diarrheal illness , and consumption of fast food were associated with infection . 
 contaminated roof - collected rainwater was also detected . 
The Study
Conclusions