Although Addington et al failed to find an association between DUP and negative symptoms, they speculated that when such an association is reported it may reflect either that negative symptoms pre-date onset and hinder help-seeking or that longer DUP itself leads to enduring negative symptoms.
A secondary case was any case-patient with date of onset >24 hours after date of onset of primary case.
The average duration of the outbreaks, determined as the first date of onset to the last date of onset, was 8.9 days (median 8; range 1 40 days).
The earliest date of onset was June 21, and the latest date of onset was August 4. Mosquito collection dates ranged from 8to5050 days after onset of illness.
Outbreaks were considered to be of the same cluster if the first date of onset in outbreakn+1 was before the last date of onset in outbreakn.
For those cases in which the real date of onset of symptoms was unknown, a proxy date of onset was estimated by subtracting two days (average of days between date of onset and date of laboratory testing in those cases in which both real dates were known) from the date of laboratory testing.
Where they could not give a precise date of onset we used an algorithm to approximate the date of onset for derivation of 'a days to relapse' variable.
When date of onset had to be estimated, the median time period (in days, by health region) between the onset and proxy date was subtracted from a case's specific proxy date and used as the estimated date of onset.
Since brucellosis infections can have symptoms that mimic other diseases and may have an unknown date of onset the date the infection was diagnosed was used in this analysis rather than the date of the onset of symptoms [ 6].
Click to enlarge - For cases with unknown onset date, detection date, confirmation date or reporting date was used.
