Klingon augment virus The Klingon augment virus was a modified form of Levodian flu that threatened to wipe out the Klingon race in the mid - 22nd century . It was inadvertently created by Klingon researcher s who were attempting to bio - engineer enhanced warriors using DNA from genetically - modified Human embryo s left over from Earth ' s Eugenics Wars . History . In 2154 , Klingon scientist s working under the direction of Antaak recovered several Augment embryos from a hijacked Bird - of - Prey destroyed in orbit of Qu ' Vat Colony during the Augment Crisis . Fearing that Humans could overwhelm the Empire if they moved to staffing their ships with Augments , a project was set up to attempt to create their own Augments to counter the perceived threat . The effort failed dreadfully . The Augments created did develop enhanced strength and intelligence , but they also began to show Human characteristics , from the blatant to the subtle . These included personality alterations and loss of the characteristic forehead ridges . Ultimately , the subjects died agonizing deaths when the incompatible DNA resulted in neural system breakdown . While working to stabilize the augmentation process , the scientific team enhanced a test subject who was , unknown to the team , also infected with Levodian flu . The flu virus in some manner incorporated the Augment DNA , turning a carefully controlled experiment into an epidemic . As the unstable augmentation process always killed the subject , this epidemic threatened the Klingon race with extinction . The virus spread very rapidly , infecting millions within months . One of the first planets struck was N ' Vak Colony . The Klingons attempted to capture Doctor Arik Soong to help develop a cure , but their efforts were thwarted by Soong ' s incarceration in a high security detention facility . They then moved to kidnap Doctor Phlox , using Rigelian intermediaries and the assistance of Section 31 agents . Phlox was forced to work with Antaak to find a cure . However , the Klingon High Council was unwilling to wait , and dispatched a fleet to annihilate the infected planets , starting with N ' Vak Colony . Afterward it set course to Qu ' Vat Colony . ( ) When it became clear to the research team on Qu ' Vat Colony that it would take weeks to develop a cure , stabilizing the augment virus became the researcher ' s primary concern . Their efforts proved successful ; a method was developed that stabilized the process in the early stages , after the cranial ridges had dissolved and some minor neural re - ordering had occurred ( which caused personality changes ) , but before the virus became contagious , enhanced augment abilities , and caused a fatal neural pathway breakdown . Eventually , Admiral convinced the High Council to call off their sterilization program of destroying the infected planets . The cure was distributed throughout the Empire . Because afflicted Klingons ' DNA had been altered by the virus , the Human appearance and genetic traits were passed onto the descendants of the infected . Initially there were millions of Klingons who had to live with the disfigurement . ( ) In 2154 , Antaak and Laneth feared that Klingons without ridges would become outcasts , lose their positions and would no longer have a place in the Empire . ( ) Klingons with forehead ridges were still encountered by the Federation during the 2250s , including all known members of the Klingon High Council , suggesting that not all Klingons were affected by the virus or that some of them were cured . ( , ) However , and despite Antaak ' s fear , by the 2260s , affected Klingons served as the captain s and crews of front - line starships in the Klingon Defense Force . ( ) Later on , some of them even achieved the title of Dahar Master and earned their statues among the Hall of Heroes on Qo ' noS . ( ) By the 24th century , knowledge of Klingons with smooth foreheads had been generally forgotten by the population of the . Also , the reason for Klingons having smooth foreheads a hundred years earlier was not widely known outside the Empire . When asked by Miles O ' Brien and Julian Bashir , Worf simply gave the answer " we don ' t discuss it with outsiders " , though Bashir immediately suspected viral mutation to be the cause . ( ) Background information . This storyline , seen in the episodes and , was intended in part to explain why TOS Klingons had a more Human appearance , and later Klingons did not . The writers also hoped the two - parter would shed some light on the change in the Klingons ' temperament and disposition between the TOS and eras . For years , unofficial explanations had appeared in " Star Trek " literature to explain the difference between the Klingons from the 1960s series and those in later productions . The idea of genetic engineering was explored heavily in several publications licensed by Paramount Pictures , among them FASA ' s " " , several Pocket Books novels ( such as " Rules of Engagement " ) , and the reference book " The Worlds of the Federation " by author Shane Johnson . These works indicated that the " Klingons " encountered during the " Original Series " era were " Klingon - Human fusions " intentionally created to make infiltration into Federation space easier ; the true nature of Klingons was revealed during the emergency transmission of the , as depicted in . In addition to the " fusion " explanation , the producers of " Star Trek : Enterprise " had heard many pitches , over the years , for aimed at explaining the change in the Klingon appearance . Additional theories included that the Klingons seen during the " Original Series " were from another race than those of later eras and also that some sort of disease was to blame . The " Enterprise " writing staff mirrored the fan community in that some felt it might be fun to account for the change , while others thought it was probably best to ignore the entire situation . The topic came up again when writer Manny Coto was named showrunner during the series ' fourth season . At first , the producers were only interested in a story with one or more " ridgeless " Klingons who had infiltrated Starfleet for the purpose of intelligence gathering . It was thought the story might involve a surgically - altered Klingon operative aboard " Enterprise , " someone like Arne Darvin a century later . Around this time , the writing staff had recently concluded the three - part Augment Crisis arc , and it occurred to them that some of the genetically - engineered embryos might have survived the destruction of the Bird - of - Prey , and that the Klingons might use these embryos to bio - engineer their own version of " Klingon supermen " . This seemed to be a way into a story dealing with the origin of Human - like Klingons . More to the point , the " Enterprise " producers thought it was simply " too cool " an idea to reveal that Kor , Kang , and other " Original Series " Klingons may have had the DNA of Khan inside them . While some fans clamored for an explanation for the " smooth forehead " Klingons , " Affliction " teleplay writer Mike Sussman hoped to do more – account for the apparent change in Klingon culture between the 23rd and 24th centuries . As depicted in the first " Star Trek " series , Klingons were notoriously savage , crafty , and at times even cowardly , putting this characterization at odds with the more noble and honorable Klingons seen in " The Next Generation " . The " minor neural re - ordering " noted by Phlox was intended to suggest that the augmented Klingons were not only " cursed " with a more Human appearance , but that they also inherited many Human weaknesses as well . In " Divergence " , the female Laneth , newly infected by the augment virus , claimed that she " felt fear for the first time since I was a child . " Her fellow augmented warriors had " become like ( Humans ) . . . weak , cowardly . " The " Enterprise " writers ' explanation for the change in the Klingons did not – and could not – satisfy every " Star Trek " fan . Gene Roddenberry himself reportedly believed any " explanation " was unnecessary ; the makeup seen in the films and the later series would have been too expensive during the 1960s . Roddenberry felt it was best to simply imagine that Klingons " always " had ridges ( although this preference was officially contradicted by canon when the change was noted by the DS9 crew in ) . According to the , genetically modified Klingons were referred to as " Metagenic Klingons " and " Metagens " in the script for " Divergence " . Furthermore , the author s of this reference work presumed that all Klingons seen in TOS were metagens . An alternative name for this virus , from the , was " Klingon metagenic virus " . The terms " metagenic " and " metagens " were from script scene descriptions for the episodes " Affliction " and " Divergence " . Apocrypha . In " The IDIC Epidemic " , an original series novel written during the airing of " The Next Generation " , a Klingon scientist , Korsal , refers to the " Imperial Race , " a reclusive breed of Klingons who retained their brow ridges . The Imperial Race has never been seen outside the Empire and its existence is largely a mystery to the Federation . The plague that is the subject of the novel is proven to be a mutated form of " The Imperial Plague , " to which the Imperial race is very vulnerable , while smooth - headed Klingons are immune . This novel contained its own partial explanation for the difference in appearance between Klingons from the " Original Series " and " The Next Generation - " to wit , that " smooth - headed " Klingons were an offshoot of the Klingon race specifically engineered or selected for contact with outside forces . In " Against Their Nature " , the first installment of the IDW Comics " " series , it is suggested that , while Phlox ' s cure removed Augment strength and Augment intelligence , those affected did retain Augment ambition , and as such they were largely responsible for the expansion of the Klingon Empire between " " and TOS , and were able to take control of the High Council . In the novel " Forged in Fire " , it is revealed that the virus did not solely affect Klingons ; the ridged Trill witnessed in – as opposed to the spotted Trill seen in and later episodes – are the result of a strain of the augment virus that managed to infect a Trill colony through visiting Klingon traders . However , the Trill seemed not to be interested in working on methods of restoring the original Trill look , with this " sub - group " having recently ( at the time the novel was set ) being re - accepted back into Trill society . The novel also reveals that the appearance of The Albino – who is not only Klingon but is in fact Kor ' s cousin – was an unintended side - effect of prenatal genetic engineering intended to cure his bloodline of the virus . In " Star Trek Online " , the cure to the Klingon augment virus is revealed . By way of the Guardian of Forever , a group of Klingons travel back to 2270 shortly after capturing Miral Paris , daughter of Tom Paris and B ' Elanna Torres . At the conclusion of the mission , Miral ' s unique DNA is used to cure the Klingons of the augment virus .