Human herpes viruses 6 -
HHV-6 has two variants, A and B.
HHV-6A seems to be implicated in ME, with significantly higher abnormal
levels seen in sufferers than to healthy controls. It works by attacking some
of the major defenses of the immune system, for example T cells, as in the case
of HIV/AIDS, which has lead researchers to propose that HHV-6 could also act as
a cofactor in the progression of AIDS.
Three possibilities for the link between ME and HHV-6:-
Human herpes viruses 6
(HHV-6), as its name suggests, is a member of the herpes family.
There are two variants,
HHV-6A and HHV-6B.As far as one can tell, HHV-6B is the more
‘common’ one of the two.
It is a common cause of the viral disease roseola that is seen in over 95% of young children by the age
of 2 - a self-limited fever and rash. Much like chicken pox and shingles, the
virus can be reactivated in adults that were infected as children. The virus
persists after the initial infection in a latent ('hibernating') form in the
cells of the central nervous system, bone marrow and immune system and it can
then reactivate and begin replicating again (Fig. 1).
MS and ME
The other strain, however, HHV-6A, is the one implicated in AIDS, MS and ME, amongst other diseases. In the case of MS, a direct link has been found between
it and HHV-6A . In addition, Dr. Dharam Ablashi, co-discoverer of HHV-6 and
Scientific Director of the HHV-6 has summarised from existing literature that
when lab methods detecting the presence of active HHV-6A infection are used, an
exceptionally strong, statistically significant association between HHV-6A and
both multiple sclerosis and ME is consistently seen.
From what I’ve
found, it seems that it is not a case of HHV-6A being reactivated in an adult
like I explained before but people with MS, ME etc. acquiring it as a primary
infection. So, they haven’t been infected as children etc. Using the chicken
pox ‘analogy’ again, it’s like when adults suffer from the chicken pox (not
having caught it as children), and of course it can be a lot worse when this
happens. They haven’t built up immunity to it.
Demonstrating latency and reactivation of the virus. 
But what does HHV-6 actually do?
HHV-6A is known to be a cytopathic pathogen with a powerful ability to infect
and kill cells. It can directly infect or interfere with the function of several
elements of the immune system including CD4 and CD8 T-cells, NK-cells, some
B-cells, and mononuclear phagocytes. Basically, it’s messing with some of the
major defences your body has towards pathogens in your body, interrupting the
normal function of the immune system. T cells, for example, are regarded as the
‘generals’ of the immune system. So this is where the problems could arise and
See Fig. 2 on the next page for an illustration of the progression of HHV-6.
SIDENOTE - HHV-6 and HIV/AIDS
The cells HHV-6 targets have brought about connections being
made with HIV/AIDS as HIV destroys the same kind blood cells - CD4 T
cells (helper cells). Findings have lead to proposals that HHV-6 acts
can be a cofactor in the progression of AIDS and in the switch of HIV
from the latent to the replicative state. Ultimately, HHV-6 can be a
cause of death in AIDS patients. HHV-6, however, does not cause AIDS
if the person is not infected with HIV. Of course, there is a lot more
information on that subject but I could write a whole book alone on this
Illustrating a progression from infection to the clinical disease 
The tendency to affect, be attracted
to, or attack nervous tissue
Disease of the blood vessels
In the end, there are three ways that HHV-6 could be related to ME:
ME is caused by this virus.
causing a persistent viral infection of HHV-6.
HHV-6 causes ME when it comes into contact with another virus,
for example parvovirus.
a. HHV-6 could be relatively harmless on its own but when it comes into contact with another specific virus it is then when the trouble occurs.
i. For example, in the case of bird flu, if a human infected with influenza virus
also acquires H5N1, a mutant strain of bird flu that can be transmitted from
human to human could form.
It is an
opportunistic pathogen that takes advantage of an already weakened immune
Whatever the case is, there is quite a lot of significant data showing HHV-6 in
ME patients compared to healthy controls.