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data on case investigation timelines in 2002 were collected from records at state and local health departments and public health laboratories in each of 6 states for < 100 salmonella spp .
participating states included 1 with a large population ( > 6 million ) , 3 with a medium - sized population , and 2 with a small ( < 2 million ) population from 5 different geographic regions .
rules mandated reporting of diagnosed cases from physicians or clinical laboratories to local health departments ( 2 states ) , to the state health department ( 2 states ) , or to both ( 2 states ) .
cases were selected by systematically choosing every nth record on the basis of the number of cases reported and the number sampled . for 1,319 cases , dates were collected for the following : onset of symptoms ( 873 [ 66% ] ) , stool specimen collection ( 1,088 [ 82% ] ) , culture result ( 633 [ 50% ] ) , report to state or local health department ( 553 [ 42% ] ) , submission of isolate to public health laboratory ( 882 [ 98% ] of 899 isolates that were submitted ) , case interview ( 648 [ 49% ] ) , and molecular subtyping by pulsed - field gel electrophoresis ( pfge ) ( 634 of 635 isolates that were subtyped ) .
although stool culture result dates were recorded for 633 cases , most were for final culture results based on confirmation by the public health laboratory .
for each case , intervals between milestones were calculated from the dates available . for 112 outbreaks of foodborne disease ,
dates were collected for the following : implicated meal or event ( 100 [ 89% ] ) , onset of symptoms of index case - patients ( 112 [ 100% ] ) , first stool collection ( 65 [ 79% ] of 82 outbreaks for which stool samples were collected ) , foodborne illness complaint or report of outbreak - related case to health department ( 99 [ 88% ] ) , initiation of outbreak investigation activities ( 90 [ 80% ] ) . for each outbreak , intervals were calculated from the dates available .
the median intervals from onset of symptoms to surveillance milestone events for individual cases were as follows ( table 1 ) : collection of stool samples , 24 days ; initial stool culture results , 58 days ; case report to health department , 79 days ; isolate submission to public health laboratory , 810 days .
for case - patients who were interviewed , the median interval from onset of symptoms to interview was 12 days for e. coli o157:h7 cases , 14 days for salmonella spp . and shigella spp .
cases , and 18 days for campylobacter spp . cases . for isolates that were subtyped by pfge ,
the median intervals from onset of symptoms to subtyping were 15 days for e. coli o157:h7 , 18 days for salmonella spp . , and 21 days for shigella spp .
* pfge , pulsed - field gel electrophoresis . a higher percentage of isolates were submitted to the public health laboratory in states where submission was required ( 98% for salmonella spp .
isolates , 100% for e. coli o157:h7 ) compared to states where submission was not required ( 75% for salmonella spp .
however , no difference was found between these states in length of time for isolates to be submitted .
of 112 confirmed foodborne disease outbreaks , 83 ( 74% ) had an etiologic agent confirmed by laboratory testing ( table 2 ) ( 5 ) . of 29 outbreaks that were not confirmed , norovirus was the suspected cause in 17 ( 59% ) outbreaks , and toxigenic bacteria were suspected in 7 ( 24% ) outbreaks .
median intervals from onset of symptoms to outbreak complaint or recognition were 1 day for bacterial toxins , 3 days for norovirus , 8 days for e. coli o157:h7 and campylobacter spp . , and 16 days for salmonella spp .
overall , 83 ( 74% ) outbreaks were detected by a consumer complaint , 12 ( 11% ) were detected by a healthcare provider , 11 ( 10% ) were detected by pfge cluster evaluation , and 6 ( 5% ) were identified through an interview with an individual case - patient .
intervals from onset of symptoms to consumer complaint ( median 3 days , range 021 days ) or to report by healthcare provider ( median 3 days , range 011 days ) were similar .
outbreaks identified by case interview ( median 11 days , range 616 days ) or pfge cluster evaluation ( median 23 days , range 783 days ) followed case surveillance timelines described above . the median interval from detection of the outbreak to the initiation of the first outbreak investigation step was 0 days ( range 041 days ) for all outbreaks .
the median duration of exposure for all outbreaks with a confirmed etiologic agent was 1 day ( range 121 days ) .
however , 12 ( 29% ) of 41 norovirus , 2 ( 67% ) of 3 e. coli o157:h7 , and 9 ( 75% ) of 12 salmonella spp .
the median duration of multiday outbreaks was 4 days for norovirus ( range 213 days ) , 5 days for e. coli o157/h7 outbreaks ( range 56 days ) , and 10 days for salmonella spp .
the multiple steps between onset of a foodborne illness and its investigation by a public health agency result in delayed recognition of outbreaks caused by reportable enteric diseases .
one important way to speed the detection of outbreaks is to encourage clinicians to immediately notify health departments when they suspect a patient is part of an outbreak . since many outbreaks caused by e. coli o157:h7 and salmonella spp .
last multiple days , physician reporting concurrent with stool collection may provide opportunities for a public health intervention that could prevent outbreak - associated cases .
the speed with which clinical laboratories receive , process specimens , and report results varies by setting , agent , and location .
the lack of detail available about these steps is an important limitation of this study .
however , health departments generally receive reports from clinicians a median of 2 days after the culture result , and isolates are submitted to public health laboratories within 23 days of the initial culture result .
these data suggest that improving physician and laboratory reporting practices and logistics could shorten the reporting timeline by 1 or 2 days for most cases .
timeline elements directly under control of public health agencies include the interval from case report to interview and from submission of the isolate to subtyping by pfge .
our results demonstrate more variability for these intervals than for earlier steps in enteric disease surveillance . in particular ,
half of e. coli o157:h7 cases but less than one fourth of salmonella spp . cases were contacted by a local health department on the same day the report was received .
in addition , outbreaks caused by e. coli o157:h7 were detected a median of 8 days sooner than outbreaks caused by salmonella spp .
given the risk for hemolytic uremic syndrome after e. coli o157:h7 infections and the potential for person - to person transmission , such attention is warranted .
even so , the intervals from onset of symptoms to pfge subtyping documented in the nationwide outbreak of e. coli o157:h7 infections associated with spinach demonstrated that little has changed across the public health system from 2002 to 2006 ( 6 ) .
infection reinforce the need to increase the timeliness of case follow - up , molecular subtyping , and the linkage of results between them that can reduce delays in the investigation of foodborne outbreaks ( 7 ) .
we reviewed timeline information for a sample of salmonella spp . 
 , shigella spp . , 
 campylobacter spp . , and escherichia coli o157:h7 cases and all confirmed foodborne outbreaks reported in 6 states during 2002 . increasing the timeliness of case follow - up , 
 molecular subtyping , and linkage of results are critical to reducing delays in the investigation of foodborne outbreaks .