within 4 days , 5 patients with skin lesions suggestive of an opv infection were reported to the infectious disease task force at the bavarian health and food safety authority .
infected patients were from 2 unrelated families living in 2 different counties in the greater munich area , germany .
the families had bought 1 and 2 rats , respectively , from the same pet shop on december 15 and december 17 , 2008 .
source tracing showed that the pet shop owner had sold a litter of 8 rats to 7 different households in the greater munich area .
the pet shop owner had purchased the litter from a bavarian rat breeder 7 days before the last rat in the litter was sold .
no symptoms of opv infection were reported in the rats or any another animal in the pet shop .
the pet shop owner denied purchasing any animals from abroad that could have been related to the 2003 us monkeypox outbreak ( 7 ) , although he did acknowledge owning another breeding facility in the czech republic .
inspection of the breeding facility in bavaria found 4 rats with crusts suspicious for opv infection .
mice , hamsters , rabbits , and degus ( octodon degus ) were also bred in the facility , but none had clinical signs of opv .
a total of 31 rats from the facility were tested for opv infection by oral swabs and serology .
according to their owners , all pet rats were asymptomatic when purchased , but 2 rats ( 1 in each family with a human opv infection ) died after 9 and 14 days , respectively .
one rat had distinct skin lesions on its extremities , mouth , and nose ( figure 1 , panel a ) ; the other had only 2 very small lesions on its front leg and nose .
two additional rats from the litter in 2 other households were euthanized due to clinical suspicion of opv infection ; 3 rats were assessed as healthy by their owners .
a ) rat named shiva ( strain named after this rat ) with lesions on the right hind limb ; it died 1 day later .
b ) neck lesions of a girl without previous vaccinia virus ( vv ) vaccination .
c ) neck lesion of the girl s grandmother with a history of vv vaccination .
2 . in households 1 and 2 ( table ) with human cases of infection , 2 and 3 persons , respectively , reported only direct skin contact with their pet rats since the first day of purchase .
notably , the onset and severity of symptoms were apparently associated with a patient s vv vaccination status : 2 girls ( patients 2 and 5 , each 16 years of age with no history of vv vaccination ) had multiple lesions on the neck , chest , and abdomen ( figure 1 , panel b ) accompanied by fever and local lymphadenopathy .
in contrast , the incubation period for 2 vv - vaccinated mothers ( patients 1 and 3 , 42 and 40 years of age , respectively ) and for the vv - vaccinated grandmother of 1 of the girls ( patient 4 , 60 years of age ) was > 7 days .
all showed less severe symptoms ( figure 1 , panel c ) without fever or lymphadenopathy and only 1 small skin lesion on the neck or chest . *
all obtained hemagglutinin open reading frames were 924 bp , and the respective sequences were 100% identical to each other ( genbank accession no .
rat 8 from the outbreak litter belonging to household 7 is missing because the rat owner could not be identified .
em , electron microscopy ; nd , not done ; na , materials not available .  for orthopoxvirus spp . in household 3
after 35 days , skin lesions developed in all of her rats , including the initially asymptomatic index rat .
, the kidney transplant patient without previous vv vaccination did not develop signs or symptoms suggestive of cpxv infection . nevertheless , we collected a blood sample and swabs from her throat and a recent rat - bite finger wound .
various specimens ( skin biopsies , crusts , oral swabs , serum , and whole blood ) obtained from 5 patients and from rats from 3 households and 31 other rats ( 939 ) from the local breeding facility in bavaria were sent to the bavarian health and food safety authority ( table ) .
skin biopsy and crust specimens were homogenized and inspected for typical opv - like particles by using by electron microscopy .
dna from all samples was extracted using the qiaamp dna mini kit ( qiagen , hilden , germany ) according to the manufacturer s instructions .
for opv dna detection , the realart orthopoxvirus lc kit ( qiagen ) was used . for species identification
, the products of a second pcr , spanning the entire open reading frame of the hemagglutinin gene ( 8,9 ) , were sequenced .
datasets were edited and aligned using bioedit ( 10 ) . blast search ( www.ncbi.nlm.nih.gov/blast/blast.cgi ) was performed to confirm species identification of the isolated strain as well as similarity with published cpxv strains .
a phylogenetic tree was constructed using the maximum parsimony method with the phylogeny inference package version 3.68 ( http://evolution.genetics.washington.edu/phylip.html ) with 100 bootstraps ; the tree was drawn with treeview version 1.6.6 ( http://taxonomy.zoology.gla.ac.uk/rod/treeview.html ) ( figure 2 ) .
opv - specific serum antibody titers were determined using an immunfluorescence test based on vv - infected cells and either an antihuman or an antirat immunoglobulin g fluorescein - labeled conjugate ( dako , hamburg , germany ) .
phylogenetic tree of the isolated cowpox virus ( cpxv ) shiva strain ( in boldface ; named after pet rat shown in figure 1 , panel a ; genbank accession no .
fj654467 ) , constructed by the maximum - parsimony method based on the partial sequences method based on the hemagglutinin ( ha ) gene , unrooted . blast search ( www.ncbi.nlm.nih.gov/blast/blast.cgi ) confirmed the identification of this strain as a cpxv strain with a unique ha gene sequence .
additional unique cpxv strains shown for comparison , by accession number : ay902307 ( cowha35e ) , ay902301 ( cowha82 ) , ay902299 ( cowha70 ) , ay902298 ( cowha68 ) , ay902297 ( cowha52 ) , ay902296 ( cowha51 ) , ay902295 ( cowha48 ) , ay902294 ( cowha46 ) , ay902289 ( cowha47 ) , ay902288 ( cowha41 ) , ay902287 ( cowha40 ) , ay902286 ( cowha37 ) , ay902279 ( cowha76 ) , ay902276 ( cowha23 ) , ay902308 ( cowha38 ) , ay902275 ( cowha22 ) , ay902274 ( cowha21 ) , ay902273 ( cowha81 ) , ay902271 ( cowha19 ) , ay902270 ( cowha18 ) , ay902269 ( cowha17 ) , ay902268 ( cowha16 ) , ay902263 ( cowha15 ) , ay902262 ( cowha34 ) , ay902260 ( cowha13 ) , ay902257 ( cowha09 ) , ay902256 ( cowha07 ) , ay902255 ( cowha63 ) , ay902252 ( cowha73 ) , ay944029 ( cpv90_ger2 ) , ay944028 ( cpv91_ger3 ) , af377886 ( cowpox virus ) , af377885 ( cpv-922 - 99 ) , af377884 ( cpv-867 - 99b ) , af377883 ( cpv-667 - 94b ) , af377877 ( cpv-1218 - 00 ) , af375090 ( cpx - ep-2 ) , af375089 ( cpx - brt ) , af375088 ( cpx-90 - 5 ) , af375087 ( cpx-90 - 1 ) , af375086 ( cpx-89 - 5 ) , af375085 ( cpx-89 - 4 ) , and af375084 ( cpx-89 - 1 ) .
besides molecularly proven wild rat - to - human cpxv transmission ( 6 ) an additional cpxv infection probably transmitted from a pet rat was reported ( 11 ) .
recently , 4 human infections acquired from pet rats were reported to the reference laboratory for poxviruses at the robert koch institute ( 12 ) .
we describe a cpxv outbreak among 5 patients caused by infected pet rats from the same litter .
cpxv infections seem to be increasing ( 13 ) , but because cpxv infections in humans and in most animals ( e.g. , cats and rats ) are not notifiable , this increase remains an assumption .
one obvious reason for an increase might be the fading cross - protective immunity to opv after the cessation of vv vaccination ( 14 ) . in our small cluster ,
the onset and severity of symptoms seemed to be correlated with vv vaccination status ; however , although patients reported similar contact with pet rats , patient age and manner of infection might confound this hypothesis ( 15 ) .
the rising popularity of pet rats might also be a point of concern in a population with decreasing cross - protection to opv and an increasing number of immunocompromised persons .
our findings emphasize the necessity to monitor opv infections in humans and all animals ( e.g. , notification requirement ) and to improve public awareness .
our outbreak investigation underlines the importance of close cooperation between human health and veterinary authorities in the management of zoonotic diseases .
 we describe a cluster of cowpox virus ( cpxv ) infections in humans that occurred near munich , germany , around the beginning of 2009 . 
 previously , only sporadic reports of cpxv infections in humans after direct contact with various animals had been published . this outbreak involved pet rats from the same litter . 
The Study
Conclusions