Pathogenesis+-+SARs

The SARS coronavirus - see "Structure - SARS" for more info

To cause infection, the SARS-CoV
 * 1) Enters the body through the respiratory tract.
 * 2) Infects the epithelial cell of the respiratory system, inducing apoptosis of various host cells. Peek titers (concentration) of the SARS virus occur on the second day after infection.
 * 3) Damages immune cells at the lymph nodes and other lymphoid tissues.
 * 4) Infects other organs as the immune system degrades, like the lungs, bones, kidneys, and digestive tract.

SARS-CoV infecting a cell:
 * 1) Attachment of the virus to the host cell: the envelope proteins on the SARS- CoV bind to the receptors on the cell membrane. The membrane of the host cell and the virus fuse.
 * 2) Replication: once inside the host cell, the capsid opens and releases the RNA so that transcription of the positive single stranded RNA can occur.
 * 3) Virus Assembly: the nucleocapsid forms and the virus matures in a membrane-bound vesicle that travels through the cytoplasm and releases the virus from the host cell.

Immune response:
 * 1) When the SARS virus is detected in the respiratory system (usually occurs around the second day of infection), cytokines and chemokines induce diapedesis.
 * 2) NK cells (Natural Killer cells), macrophages, and dendritic cells migrate into the area of infection (the lungs).
 * 3) Around day 7 antibodies can start being detected. These antibodies neutralize the SARS virus so that it cannot infect other cells.

Host responses with regard to time: