we conducted a retrospective cohort study of all persons who had been potentially exposed to infectious material by handling live and dead poultry , poultry products , or litter derived from infected premises .
our objective was to measure associations between potential exposure to infectious material , completeness of use of ppe , and taking and timing of oseltamivir prophylaxis with having symptoms consistent with or confirmed as resulting from influenza virus a ( h7n3 ) infection .
we pretested and then administered a questionnaire by telephone after poultry culling ended ( median 66 days , range 60143 days ) . for persons who did not respond to the questionnaire ( n = 39 ) , we extracted data recorded in the outbreak records to describe their activities in relation to the outbreak , their use of oseltamivir prophylaxis , and their seasonal influenza vaccine status .
only persons who were interviewed and completed the questionnaire ( n = 103 ) were included in the statistical analysis .
persons were invited to provide an acute - phase blood sample during the outbreak and a convalescent - phase sample 28 days after their last potential exposure .
possible case - patients were those who reported conjunctivitis or influenza - like symptoms ( > 1 of the following : fever , sore throat , cough , shortness of breath , body / muscle pain , runny nose ) in the 7 days after last potential exposure . confirmed case - patients were those for whom virus was detected by culture and rt - pcr of material from the conjunctiva or respiratory tract and/or confirmed by serologic testing .
influenza virus ( h7n3 ) from the conjunctiva of the index case - patient was prepared by growth in embryonated eggs .
serum samples were screened by using microneutralization ( mn ) and hemagglutination inhibition ( hi ) tests ( 2,3 ) .
when either test gave a positive result , we performed confirmatory western blot analysis , using purified influenza ( h7n3 ) virus ( 4 ) .
we calculated odds ratios ( ors ) , 95% confidence intervals ( cis ) , and p values for being a possible or confirmed case - patient .
independent variables are shown in the technical appendix , table a. all risk factors with p<0.2 in the single - variable analysis were initially included in a logistic regression model and then removed , least significant first , until all had p<0.1 . confounding variables ( those that caused > 10% change in the ors of covariates ) were retained regardless of p value . in total , 142 persons were potentially exposed .
questionnaires were completed for 103 ( 73% ) persons ( 21 could not be contacted , 10 declined , 7 had no contact information , and 1 questionnaire was lost ) .
characteristics , potential exposures , and preventive measures differed little between persons who did or did not complete the questionnaire ( table 1 ) .
of 46 persons who reported symptoms , 19 reported conjunctivitis with influenza - like symptoms and 27 reported influenza - like symptoms only .
always used " were protective coveralls ( 81% ) , protective footwear ( 82% ) , disposable gloves ( 67% ) , face - fitted mask ( 51% ) , other mask ( 24% ) , and protective goggles ( 19% ) ( technical appendix , table b ) . *
median age ( range ) 40 ( 1564 ) y.  median age ( range ) 41 ( 1974 ) y.  for the 39 persons who did not respond to the study questionnaire , we used activities recorded in the outbreak records .
high exposure includes > 1 of the following activities : entering poultry sheds , coming within 1 m of live poultry , handling live or dead poultry , contact with chicken litter or feathers , and handling eggs or egg products . 
complete use of personal protective equipment defined as always using gloves , coveralls , footwear , face - fitted n95 respirator , or other mask ( unspecified ) , and goggles . 
# reported by the 27 patients with influenza - like symptoms only and the 19 with conjunctivitis and influenza - like symptoms .
fifty - six ( 54% ) persons reported complete use of ppe . single - variable analysis indicated that working on an infected premise ( or 2.76 , 95% ci 1.176.50 ) was significantly associated with being a possible or confirmed case - patient ( technical appendix , table a ) .
higher levels of exposure to potentially infected poultry ( or 2 . 20 , 95% ci 0.965.04 ) and only partial use compared with full use of ppe ( or 2.16 , 95% ci 0.974.83 ) were also associated with being a possible or confirmed case - patient , but 95% cis were < 1.0 .
characteristics not associated with being a possible or confirmed case - patient were age > 30 years ; male sex ; being a department for environment , food and rural affairs employee ; smoking ; having had a prior influenza vaccination ; timing of starting oseltamivir prophylaxis ; and exposure to potentially infected poultry in the preceding months .
multivariable analysis showed the association with being a possible or confirmed case - patient to be statistically significant for incomplete use of ppe and weakly significant for working on an infected premise ( table 2 ) . * based on 96 questionnaires with complete information .
ci , confidence interval ; defra , department for environment , food and rural affairs .
serum samples were available from 91 persons : 33 acute- and convalescent - phase pairs , 49 acute - phase samples , and 9 convalescent - phase samples .
only the serum from the index case - patient showed reactivity in both the mn ( titer 40 ) and hi ( titer 32 ) tests and also showed reactivity in western blot .
all other acute- and convalescent - phase samples were negative in both tests . during the outbreak , eye , nose , and
throat swabs were taken from 14 persons ( 18 days after symptom onset ) ; 10 reported influenza - like symptoms ( 2 without eye involvement ) , 2 reported no symptoms , and 2 had no clinical information available .
comprehensive molecular diagnostic tests for common human viral respiratory pathogens ( enteroviruses , rhinoviruses , adenoviruses , respiratory syncytial viruses , parainfluenza viruses ) were also performed and did not provide evidence of alternative causes of infection .
a vaccine strain of avian paramyxovirus ( newcastle disease virus ) was recovered from 1 person with conjunctivitis , which suggests that at least 1 case of conjunctivitis was caused by avian paramyxovirus .
serologic testing for seasonal influenza infection ( hi tests on all paired serum samples ) did not indicate any recent human infections .
because workers were interviewed a minimum of 2 months after the outbreak , they may not have accurately recalled their exposures .
in addition , we relied on self - reported data . difficulties recalling symptoms were less likely as we actively followed up persons for 7 days after last exposure . in the absence of a control group , such as farmers from noninfected premises ,
whether the incidence of influenza - like illness and conjunctivitis in this cohort was different is unclear , although during the outbreak , influenza activity in the general population was low and no isolates of seasonal influenza were reported .
we did not measure dust exposure as an alternative explanation for conjunctivitis in some or all persons , apart from the index case - patient who reported this symptom .
the results from laboratory testing were limited because convalescent - phase serum was not available from all persons who reported influenza - like illness . however , a wide range of molecular diagnostic tests for human viral pathogens were performed on samples from persons who were not well at the time of the outbreak .
because the kinetics of appearance and disappearance of human antibodies to avian influenza are poorly understood , timing of the collection of samples may not have been optimal in this outbreak and we may have missed the opportunity to diagnose some infections . moreover , because serologic tests for influenza virus a ( h7n3 ) may not correlate well with infection ( 5 ) , we could not rule out influenza a virus ( h7n3 ) infection among symptomatic persons , even in the presence of convalescent - phase serum that was negative for h7 .
strict compliance with ppe use should be reinforced when outbreaks of avian influenza among poultry are being managed , as recommended in current guidance from the united kingdom ( 6 ) and the european centre for disease prevention and control ( 7 ) .
compliance tends to be suboptimal ( 8) , possibly because of low risk perception among poultry workers ( 9 ) .
our study suggests that rigorous use of ppe by persons managing avian influenza outbreaks reduces influenza - like symptoms and conjunctivitis and potentially hazardous exposure to infected poultry materials .
 an outbreak of avian influenza ( h7n3 ) among poultry resulted in laboratory - confirmed disease in 1 of 103 exposed persons . incomplete use of personal protective equipment ( ppe ) was associated with conjunctivitis and influenza - like symptoms . 
 rigorous use of ppe by persons managing avian influenza outbreaks may reduce exposure to potentially hazardous infected poultry materials . 
The Study
Conclusions
Supplementary Material