on january 2 , 2011 , an 8-month - old girl with acute respiratory distress was seen in the emergency department of the children s hospital of the university of cologne .
the girl s parents had noticed labored breathing , intercostal retractions , and fever for 1 day .
no one else who had contact with the girl was sick . at admission , the girl was lethargic and inappetent with a fever of 38.3c and oxygen saturation of 86% .
the patient had submandibular lymphadenopathy and mild pharyngitis but no rash or abnormalities of the heart or abdomen .
the clinical signs were typical of an upper respiratory tract infection combined with severe obstructive bronchitis .
chest radiographs showed diffuse bilateral infiltrates and total atelectasis of the right upper lung lobe .
blood analysis indicated partial co2 concentration within normal limits and slightly elevated c - reactive protein level ( 10 mg / l ) .
electrolytes and renal and hepatic markers were within reference ranges , as was complete blood count except for thrombocytosis ( 744,000 platelets/l ) .
treatment with prednisolone and inhalation therapy delivering albuterol and ipratropium by vaporizor was initiated . because of the lung atelectasis , the child received cefuroxime as prophylaxis for 2 weeks .
oxygen saturation could be restored to within reference limits with nasal cannula oxygen delivery at 4 l / min . during the next 2 days , the patient s body temperature was 38.0c39.0c , and she remained lethargic . a nasopharyngeal aspirate was obtained 4 days after symptom onset and screened for respiratory viruses by real - time pcr ( 2 ) and luminex xtag rvp panel ( abbott , wiesbaden , germany ) .
each assay had positive results for hbov dna and negative results for influenza a virus ; influenza a virus subtype h1n1 ; influenza b virus ; parainfluenza viruses types 14 ; adenovirus ; human metapneumovirus ; coronaviruses nl63 , hku1 , 229e , and oc43 ; respiratory syncytial virus ( rsv ) ; rhinovirus ; and enterovirus .
cultures of blood collected on the day of admission , before antimicrobial drug treatment was started , were negative .
a second chest radiograph showed partial atelectasis of the left upper lung lobe , a retrocardial infiltrate , and pneumomediastinum . on hospitalization day 5 , oxygen saturation
could be maintained at a lower flow rate . on day 6 , chest radiograph showed regression of atelectasis in both lobes and of the pneumomediastinum .
temperature dropped to subfebrile levels , and the child s general condition was improving . on day 9 , no additional oxygen was needed . on day 10 ,
chest radiograph showed residual atelectasis in both upper lobes and residual infiltrates in both lungs , and the patient was discharged .
two weeks later , at follow - up examination , the child was doing well , breath sounds were unremarkable , and the pathologic radiographic findings had resolved completely . to verify that the disease was caused by an hbov infection
, we performed a real - time pcr targeting the nonstructural protein 1 region of hbov ; we detected 5,819 copies / ml hbov dna in the patient s serum 30 days after symptom onset ( 3 ) .
the pcr was conducted with primers os1 and os2 as described ( 4 ) , and an hbov subtype 2 plasmid dilution series ( kindly provided by tobias allander , karolinska institute , stockholm , sweden ) was used as a quantitative control .
sequencing was performed by an external sequencing service ( eurofins mwg , munich , germany ) ; the same primers from both directions were used .
sequencing and blast analysis ( http://blast.ncbi.nlm.nih.gov/blast.cgi ) confirmed the virus to be hbov1 , not hbov24 .
additionally , hbov - specific igm and igg and avidity of igg were measured by sensitive and specific enzyme immunoassays ( 5,6 ) .
results were clearly positive for both : igm absorbance 0.385 and cutoff 0.167 ; igg absorbance 2.971 and cutoff 0.188 .
igg was of low avidity ( 4% , cutoff 15% ) , indicating acute primary hbov infection .
large - scale studies showed that hbov can be detected in children with signs and symptoms of respiratory tract infection .
studies have detected hbov in 9% and 19.3% of all samples , indicating that it is the second or third most commonly detected virus , after rsv and rhinovirus ( 2,10 ) .
thus , the overall contribution of hbov to all detected respiratory viruses lies well below that of rsv .
high prevalence does not necessarily mean high clinical relevance , and proving its causative role has been difficult because the virus is often detected along with other viruses ; co - detection rates are as high as 75% ( 11,12 ) .
hbov can also persist for months in the respiratory tract after resolution of disease , further complicating diagnosis ( 12 ) , which therefore should be based on detection of hbov dna in blood and measurement of hbov - specific antibodies .
hbov is the most probable cause of respiratory tract disease if the patient has a high viral load in nasopharyngeal aspirates accompanied by viremia , if hbov is the only pathogen detected , and if an acute primary hbov infection is diagnosed by serologic testing ( 5,11,13 ) .
the serologic assay developed earlier was validated in a series of studies and shown to reliably measure serologic response against hbov ( 58 ) .
however , the contribution of bacteria to the course of the disease can not be completely ruled out .
signs and symptoms for the patient reported here have been described as the most common signs and symptoms of hbov - infected children ( 14 ) and are typical of lower respiratory tract viral infections in general . in 1 study
( 14 ) , 18 patients had an hbov single infection and 2 had lobar atelectasis , as did the patient reported here .
similarly , another case report described hbov infection that resulted in pneumomediastinum ( 15 ) .
the age of the patient reported here is also typical of hbov , which mostly infects children 6 months to 3 years of age , but it does not usually infect young infants , as rsv does ( 14 ) .
the case reported here shows that a lower respiratory tract infection caused by hbov can lead to severe and life - threatening disease .
 human bocavirus ( hbov ) , discovered in 2005 , can cause respiratory disease or no symptoms at all . 
 we confirmed hbov infection in an 8-month - old girl with hypoxia , respiratory distress , wheezing , cough , and fever . 
 this case demonstrates that lower respiratory tract infection caused by hbov can lead to severe and life - threatening disease . 
The Patient
Conclusions