Infection

A viral infection can be caused by either being bitten injection, or any other way managing it to enter the blood stream. Host is a term for a person or creature infected with the T-Virus.

Inhalement
Inhaling airborn "T" cells has the longest infection rate. This form is only read about in files. It apparently rots away the skin. When the initial outbreak occured in the Research Facility, the researchers all had to wear suites for several days, causing lumps to appear. The lumps eventual became more and more itchy until the rotten flesh would just come loose and fall off. It is soon followed by insanity, and eventualy cannibalism (some files in the origonal and remake involve a murder, followed by "tasty").

Zombie - human infection
This form of infection can last upto several hours before transforming the host into a zombie, however just because it can last several hours doesn't mean it can't last several minutes as seen in Resident Evil: Outbreak.

Leech - Human Infection
Being Leeches, they feed via sucking the blood of creatures, allowing the Leech to infect faster. between the attack on the train and the discovering of the zombies by Rebecca Chambers, is would take less than 2 hours, maybe even minutes. Sometimes the leeches will stay on the body making a 'Leech Man' which will turn into a Zombie within minutes, with the Leeches still hanging on.

Cerberous - Human Infection
Cerberous alays travel in packs. Due to their cainine instincts, they will all eat the kill. Due to packs being at a maximum of 10-14 (explained in files), it would be more likely of the human dying and their body being too damaged to ressurect.