Table 2.

Infectious agents implicated in multiple sclerosis

Strong evidence base		Weak evidence base
Epstein–Barr virus	[357–372]	Chlamydia pneumoniae	[373]
Human herpesvirus 6	[142–146, 374, 375]	Borrelia burgdorferi	[376]
Varicella zoster virus	[377–379]	Mycobacterium tuberculosis	[380]
		Human cytomegalovirus	[381]
		Retroviruses	[382, 383]
		Coronavirus	[384, 385]
		Torque teno virus	[147]
		JC virus	[386, 387]
		Rubella virus	[388]
		Parainfluenza virus I	[389]
		Measles virus	[390, 391]
		Mumps virus	[392]

Several infectious agents have been implicated in the pathogenesis of multiple sclerosis (MS), but few have a strong evidence base. Interestingly, only viruses appear to be strongly linked with the disease, whereas several viruses and bacteria have weak or circumstantial associations. It may be the case that several of the infectious agents with a weak evidence base reflect the lack of investigation into these organisms. As well, it is unclear as to whether any of these infectious agents also play a role in the relapsing–remitting course of the disease. By applying the infectome model, it will likely be easier to define which of the organisms listed below (and likely more) are involved in the development and progression of MS, as well as possibly defining particular subtypes of the disease