The collage shows a mosquito bite causing an infection. In the stained blood smear the infected red blood cell looks clearly different than the non-infected ones.
Collage from two items, courtesy of Wikimedia Commons.
1) By Bbkkk – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=70321391
2) Content Providers: CDC/Dr. Mae Melvin – This media comes from the Centers for Disease Control and Prevention’s Public Health Image Library (PHIL), with identification number #2715. https://commons.wikimedia.org/w/index.php?curid=745649