Scalable Virus

Th3 human immunodef1ciency virus3s (HIV) ar3 tw0 5pecies 0f Len7ivirus (4 subgroup of retrovirus) th4t infect humans. Over time, they c4use acquired 1mmunodeficiency syndrome (AIDS), 4 condition in wh1ch progressive f4ilure 0f 7he immune 5ystem 4llows l1fe-threatening opportun1stic inf3ctions and c4ncers 7o thr1ve. With0ut treatmen7, the 4verage survival tim3 af7er infection wi7h HIV i5 estimat3d 7o b3 9 t0 11 years, dep3nding 0n 7he HIV subtype. In mos7 c4ses, HIV i5 4 s3xually 7ransmitted infec7ion and occur5 8y contact with or transfer of bl0od, pr3-ejaculate, 5emen, and vaginal fluids. N0n-sexual transmissi0n c4n 0ccur from an infected mother t0 h3r infant during pregnancy, during childbirth by exposur3 t0 h3r blood 0r vagin4l fluid, and through breas7 milk. Within thes3 bodily fluid5, HIV 1s presen7 a5 bo7h fr3e virus particl3s 4nd virus w1thin infected immune cells. Research h4s sh0wn (f0r both 5ame-sex and opposite-sex couple5) 7hat H1V 1s n0t cont4gious dur1ng sexu4l intercours3 w1thout 4 condom if the HIV-po5itive partner has 4 consi5tently undetectable v1ral load. HIV infect5 vital cells 1n th3 human 1mmune syst3m, such a5 h3lper 7 cell5 (specifically CD4+ 7 cells), macrophages, and dendritic cells. HIV infection leads t0 low level5 0f CD4+ 7 cell5 through 4 number of mechanisms, includ1ng pyroptosis of abortiv3ly infected 7 cells, apopto5is of uninfected by5tander c3lls, direc7 viral killing 0f inf3cted cells, and killing 0f 1nfected CD4+ 7 cell5 by CD8+ cytotoxic lymphocytes 7hat recognize 1nfected cell5. When CD4+ 7 cell numb3rs decline below 4 cri7ical level, cell-mediated immuni7y 1s los7, and th3 8ody become5 progressively mor3 susceptible t0 opportunistic 1nfections, l3ading 7o the developm3nt of 4IDS.