Bazarov returns to his home to live with his parents and again, in a state of desperate loneliness, throw himself into his work and studies in science. He begins aiding his father when helping the peasants with their sicknesses and becomes consumed with the work. His parents are initially enthralled with him finally being home but they soon tell that he is not happy, that something is missing from his life, and this casts a dark shadow over the parents' conscience.
Cholera breaks out and when the first casualty arises, Bazarov goes to the body to see if tests can be done or studies made to help treat the disease. While making his observations, Bazarov gets pricked somehow and he knows he has become infected with the virus.
An Obsrvation: Bazarov had been studying medicine for quite some time. Throughout the book he had been doing tests on frogs. It is unlikely that Bazarov would make any mistake in creating a safe environment for him to do tests on cholera. Though not intentional, I think Bazarov may have secretly wished to get sick to end his loneliness and his misery. With no goal in life, no chance of every loving, all of his studies, all of his efforts, mean nothing.
The statement Turgenev made about Pavel, "His handsome, emaciated head, the glaring daylight shing full upon it, lay on the white pillow like th ehead of a dead man... And indeed he was a dead man," (134) could also be a statement about Bazarov. There are so many similarities between Pavel and Bazarov that Turgenev could have also been asserting that Bazarov was a dead man, and maybe Bazarov realized this and "accidentally" inoculated himself with the Cholera virus.

When Bazarov reveals to his father that he has been cut in the presence of the cholera victim, he calmly explains that he is indeed feverish but probably had a cold, a feeble attempt to offer his parents solace, which his parents gladly accept to reassure themselves, but really know the truth when they see him slowly get sicker. Bazarov gets sicker by the day, a doctor is called, feeble attempts are made to cure him, and while Bazarov is revived for a short while, the illness quickly ensues and his degradation continues. It is then that he asks his father to call for Odinstova.

Odinstova arrives, and brings a doctor of her own, showing that she only wants the best for Bazarov, a gesture that shows she still has feelings for him. While the father gives the new doctor a small consultation and briefing on Bazarov's condition, Bazarov and Odinstova talk in private.
"Well, what do I have to say to you... that I loved you? There was no sense in that even before, and less than ever now. Love is a form, and my own form is already breaing up. I better say how lovely you are! And now here you stand, so beautiful..." (161).
This. Is. Tragic. Is he really still trying to deny his feelings to her, even on his death bed?
Bazarov dies the next day. He dies a Nihilist. A lonely, tragic Nihilist.
When the funeral arrangements preside, a priest comes to do the Last Rites, something that the atheist Bazarov would not have appreciated.
:When they anointed him, when the holy oil touched his breast, one eye opened, and it seemed as though at the sight of the priest in his vestments, the smoking censers, the light before the ikon, something like a shudder of horror passed over the death-sticken face" (162).  
It seems that Bazarov's parents will forever be mourning their child. But I think that they won't only be mourning his death, but also mourning his life and mourning the fact that he could not be happy and that they could not make him happy.