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during november 2012june 2014 , a total of 177 international travelers returning to ontario were considered persons under investigation ( puis ) for mers - cov , according to the guidelines of the ontario ministry of health and long - term care ( 6 ) .
puis were recommended to be isolated and screened for mers - cov and other respiratory pathogens ( 6 ) .
nasopharyngeal swab samples and , for persons on ventilators , bronchoalveolar lavage specimens were collected from patients and submitted to public health ontario laboratories ( phol ) , the provincial reference laboratory for mers - cov testing ( 6 ) .
fecal specimens were collected when patients had diarrhea , and urine was collected during early phases of the outbreak when appropriate specimen collection standards were ill - defined ( 6 ) .
mers - cov real - time reverse transcription pcr ( rrt - pcr ) targeted regions upstream of the e gene and within open reading frame 1b , as recommended by who ( 8) .
influenza rrt - pcrs targeted the influenza a matrix gene and influenza b nonstructural 1 gene using centers for disease control and prevention ( cdc ; atlanta , ga , usa ) protocols . if the rrt - pcr was positive for influenza a virus , we conducted subtyping for seasonal influenza a(h3n2 ) virus hemagglutinin gene ( cdc assay ) and influenza a(h1n1)pdm09 virus neuraminidase gene ( in - house assay ) ( 9 ) .
respiratory specimens were further tested by using seeplex rv15 ace multiplex respiratory viral assay ( seegene inc . ,
targets included human rhinovirus , enterovirus , influenza a and b viruses , parainfluenza viruses 14 , respiratory syncytial virus a and b , adenovirus , bocavirus , human metapneumovirus , human coronavirus oc43 , and human coronavirus 229e / nl63 .
mycoplasma pneumoniae and chlamydophila pneumophila testing was conducted by using propneumo-1 multiplex assay ( gen - probe inc . , san diego , ca , usa ) .
pcr was conducted for legionella species by using a protocol developed by cdc ( 10 ) ; binaxnow legionella urinary antigen test ( binax inc . , portland , me , usa ) was also conducted to test for l. pneumophila serogroup 1 .
of 177 puis ( mean age 48.1 years , range < 188 years ; 56% male ) , 54.8% returned from saudi arabia or uae .
identification of puis peaked after the october 2013 hajj and after the first 2 mers - cov cases were imported into the united states in may 2014 ( figure ) .
all puis had ari ; of the 85 puis for whom data were available , 47 ( 55% ) and 74 ( 87% ) had respiratory specimens collected within 5 and 14 days ( median  4 days ) from symptom onset , respectively .
specimens collected were as follows : 185 upper respiratory , 10 lower respiratory , 98 urine , 97 blood , 11 fecal , and 1 pleural fluid .
symptom onset varied from 17 days before return to 10 days after return ( median < 1 day after return ) for the 20 puis for whom this information was supplied .
one patient was excluded from the time - to - collection analysis because the specimen was collected under extenuating circumstances : testing was conducted because of worsening respiratory symptoms beginning 57 days before the patient returned from overseas .
puis and counts of major respiratory pathogens identified in travelers returning to ontario , canada , from countries affected with middle east respiratory virus coronavirus , december 2012june 2014 .
pui , persons under investigation . at least 1 respiratory pathogen ( bacterial or viral ) was detected in 89 ( 50.3% ) puis ; however , for most ( 87 [ 98% ] of 89 ) patients , only viral pathogens were identified ( table ) .
influenza was the most common virus identified : 27 ( 15.3% ) persons tested positive for influenza a , 14 ( 7.9% ) for a(h3n2 ) and 13 ( 7.3% ) for a(h1n1)pdm09 ; 14 ( 7.9% ) tested positive for influenza b. rhinovirus was also common , detected in 35 ( 19.8% ) persons , with a peak in the fall , in keeping with its seasonality in canada ( figure ; 
 table )
. similarly , influenza a(h3n2 ) peaked in the fall , whereas influenza b and a(h1n1)pdm09 peaked in late spring .
* cov , coronavirus ; mers , middle east respiratory virus ; na , not applicable . 
among the 177 returned travelers , no respiratory pathogen was found for 88 ( 49.7% ) . among the remaining 89 ( 50.3% ) returned travelers , at least 1 respiratory pathogen was found ; 12 ( 6.8% ) of these persons had viral co - infections . among the 12 co - infections were 8 rhinovirus co - infections ( 4 persons with influenza a and 1 each with influenza b , enterovirus , cov oc43 , parainfluenza ) ; 1 influenza a 
cov oc43 co - infection ; 1 influenza b  respiratory syncytial virus ; 1 cov 229e / nl63adenovirus ; and 1 cov 229e / nl63human metapneumovirus co - infection . 
given the relatively low volume of travelers arriving to canada and ontario from mers - cov  affected areas ( 0.6% of total global travel from mers - cov  affected areas entered canada during june  november , 2012 , and < 50,000 nonresident travelers entered ontario from affected countries in 2012 ) and lower rates of human - to - human transmission , risk of importation to ontario and subsequent local spread is likely low ( 1,13 ) .
although the risk for mers - cov importation is low , respiratory virus infections acquired abroad or locally after returning to canada might be relatively high and consistent , occurring in 87 ( 49.2% ) of 177 puis during the study period .
most influenza b cases were detected shortly after the 2014 ontario peak ( phol , unpub .
furthermore , 75% of puis with influenza b reported symptom onset within 4 days after their return , possibly indicating local acquisition .
similarly , puis with enterovirus or rhinovirus detected probably acquired disease in canada , given the short incubation period ( mean 1.9 days ) of rhinovirus ( 14 ) .
because limited information about clinical severity or outcomes was reported to phol , we were unable to report on the clinical spectrum of pui presentation .
furthermore , pathogens were not identified for all samples , possibly because of delays between symptom onset and specimen collection , sampling technique , or other factors .
the number of puis with influenza ( 41 [ 23.2% ] ) , whether acquired locally or abroad , is of particular concern .
influenza vaccination should be a priority for all persons and should be recommended by health care practitioners who advise travelers .
in addition , surveillance should continue for other respiratory pathogens so that their effects on health systems , when they co - circulate with emerging pathogens with similar clinical presentation , can be better understood .
we examined which respiratory pathogens were identified during screening for middle east respiratory syndrome coronavirus in 177 symptomatic travelers returning to ontario , canada , from regions affected by the virus . 
 influenza a and b viruses ( 23.1% ) and rhinovirus ( 19.8% ) were the most common pathogens identified among these travelers .