It started as a solution to lack of fertility in pandas. Scientists encoded a bloodborne pathogen with the ability to extend the fertility window of female pandas, put male pandas in the mood, and to cause the female pandas to give birth to more young (at least 2-8 pandas per birth). It seemed like a stroke of genius at the time: the disease in question only affected pandas and was only bloodborne, or so we thought until the first patient, Rebecca Brookes came in. She was a petite redhead with a severely swollen abdomen, looking as if she was 40 weeks along with triplets. She complained of headache, backache, fever, nausea in the early morning, spontaneous lactation, hyper arousal, hyper senses, and rapid swelling of her body. When asked if she could be pregnant, she shook her head, saying that there was no way she could be pregnant, and certainly not this soon. Of course the hospital still had her take a pregnancy test, and of course it showed up positive. She denied the prognosis up until she was fully dilated and pushing out her first child.
Her second and third children were met with confused acceptance that this was happening. Once she had finished giving birth and had rested a bit, she had told a nurse something which was not believed: that her symptoms started that morning. Two days later word got around to the doctors, who diagnosed her with cryptic pregnancy, pregnancy denial, and possible pregnancy psychosis. On the third day, as they were preparing her paperwork for her to be moved to the psychiatric wing, she complained of headache, and backache. Soon her temperature jumped from 98.6 to 99 degrees Fahrenheit (37-37.22 degree Celsius). Her breasts started to swell a little more, and soon you could see her stomach, which had barely gone down from her recent birth, start to swell again as well. By the next morning, Rebecca Brookes had given birth to another two children. This cycle kept repeating for about 2 weeks and a half weeks, with her giving birth 5 times, each time with at least 2 babies and at one point, a set of quints.
She was kept under observation after that. She did not get spontaneously pregnant after those two weeks, but she was in a near constant and feral state of arousal, flirting with any men she saw in the vicinity (and even some of the women). She did not have success in her endeavor for another two weeks. By that time 5 more women came in, suffering the same fate as her. A young intern eventually fell for her charms, sending her into another two week bout of pregnancy and birth. Soon the story had unfolded: A zookeeper by the name of Jose Ferriero had gotten bitten by a horny panda. He had begun to come down with a fever, chills, and a case of impossible arousal. He had had intercourse with Rebecca, flooding her womb with sperm that kept her pregnant for two weeks. Unfortunately his ejaculation into her womb was not enough to sate him, as after she left to go to the hospital he had sex with at least 3 more women.
Thus started the strangest and most feared STI in the world: The Dagan Virus. The Dagan Virus (sometimes called Dagan-13) created a state of hyper fertility to whoever caught the disease. Those who had external genitalia came down with fever, chills, increased pheromones, hyper arousal, and increased ejaculation. If they were unable to ejaculate in a partner with a womb, they would need to masterbate at least 15-20 times daily or else their gonads would fill painfully. When their ejaculate was brought to the lab, it was determined that the semen had high numbers of sperm and excellent motility. They produced as much as 1-8 ounces of semen per ejaculation, depending on how many times they were able to cum. The sperm would spread the virus to anyone with a womb, causing pregnancy in even the most barren of them.
Those with internal genitalia came down with fever, headache, sore and swollen breasts, hyper arousal, and increased fecundity. These subjects would flirt with others until they found someone who would ejaculate in them. They could be easily impregnated even by semen that had low numbers of sperm and poor motility. They would give birth every 3 days for two weeks until the sperm had impregnated all the released eggs. Then the process would start all over again.