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Report From Paris: Peterson Reports Antiviral (Vistide) Effective in Treating Herpesvirus Infected Chronic Fatigue Syndrome (ME/CFS) Patients

PetersonPhoto right

“These results show objective endpoints, subset selection, and recovery. There were complete responders and partial responders among severely ill CFS patients with HHV6 or CMV. These are encouraging results for this subset and further well-designed trials should be pursued to confirm them.” Dr. Dan Peterson

At the HHV6 Conference in Paris, France today Dr. Peterson reported on the results of a retrospective study following 65 severely ill chronic fatigue syndrome patients given a course of Vistide from 2005-2012 for HHV6 and/or HCMV infections.  Despite the interest in pathogens in ME/CFS, antiviral studies are rare and this is the first one reported for this drug.

Virus from vistide presentation

Dr. Peterson has three decades of experience treating immunologically challenged ME/CFS patients.

Vistide (Cidofovir) gets a lot less press than other antivirals and immunomodulators (Ampligen, Rituximab, Valcyte,  Valtrex) used in this disorder  probably because the drug requires a  complex infusion protocol,  frequent blood tests because of the rare but real possibility of  serious kidney side effects and is expensive  (although it can be covered by insurance).

This combination – infusions, frequent blood tests and expense – requires close physician follow-up. With Dr. Peterson’s specialized focus on patients with dysfunctional natural killer cells, however, he may be most consistent about testing for herpesviruses, which are known to be active in ME/CFS patients.

After three decades of focusing on immunologically challenged ME/CFS patients, Peterson may be more experienced at pathogen detection and treatment than any other practitioner in the field, and so it’s not surprising to find the first Vistide study coming from his office.  In an interview, a former patient of his said, ‘he leaves no stones unturned’; when he finds something he goes after it ‘aggressively’.

In his presentation he stated  almost 30% of  his patients test positive for  active HHV-6 or human cytomegalovirus (HCMV) (PCR, rapid culture, antigenemia), and a whopping 50% test positive for active Epstein-Barr virus (EBNA) infection.

Serious Drug For A Serious Illness

Vistide (Cidofovir) is  FDA approved for the treatment of cytomegalovirus (CMV) in patients with AIDS. (Cytomegalovirus is a member of the herpesvirus family.) and it’s been used off-label to treat  human papillomavirus, BHK virus, herpes simplex virus, vaccinia virus infections. The Black Box warning on Vistide speaks for itself

 ‘Cases of acute renal failure resulting in dialysis and/or contributing to death have occurred with  few as one or two doses of Vistide. The “recommended dose, rate, frequency of Vistide injections must not be exceeded.”

The Study

A positive response was denoted by a negative pathogen test, improved fatigue and cognitive functioning determined by an interview with Dr. Peterson and  the patient’s self reports after the trial.


  • Full Responders – Patients were deemed to be full responders if they were able to completely return to work or to work-related activities
  • Partial Responders – demonstrated significant improvement of symptoms but were unable to return to work or work related activities.
  • Non-Responders – Did not demonstrate any measurable improvement post-treatment


Seventy percent patients improved

Seventy percent of ME/CFS patients with HHV6 and/or HCMV infections improved significantly on Vistide

Dr. Peterson reported that seventy percent of patients were full  (able to return to work) or partial (significant increase in functionality) responders; a very high rate of success in a illness characterized by a poor response to treatments.  Only thirty percent of Vistide recipients did not have a significantly positive response to the drug. No serious side effects were seen; ironically the minor side effects seen were attributed to a drug, Probocenid, used to ensure Vistide was safe.

It’s not clear what percentage of ME/CFS patients will test positive for HHV6 or cytomegalovirus in other practices but this type of response suggests the drug may be  being under-used. With the FDA Stakeholder’s meeting  coming up in three weeks and the Chronic Fatigue Initiative’s pathogen discovery study results due to be published later this year, Dr. Peterson’s presentation is timely. (Unfortunately, Dr. Peterson was not invited to present at the FDA Stakeholder’s Meeting.)

Dr. Peterson called for placebo-controlled, double-blinded multi-center studies that address Vistide’s efficacy, examine its effects on the immune system and study the mechanisms of increase in VO2 max scores in ME/CFS.

Sample Cases

Dr. Peterson reported on several cases, all of whom were men – something Dr. Peterson has said he likes to do to break up the notion that only women get this disorder.

  • A 27 year old college graduate  unable to work because of  constant flu-like symptoms, weakness and marked cognitive decline (math!) presented with low NK functioning, low VO2 max and HHV6 and cytomegalovirus infection. He was able to return to work after 24 weeks of bi-weekly infusions. His VO2 max on the exercise test went up went up 23%,  his NK cells a remarkable 400% and he tested negative for both viruses at the end of treatment. He had had ME/CFS for three years.
  • A 54 year-old former high school teacher unable to work due to extreme fatigue, flu-like symptoms and cognitive problems severe enough to keep him from being able to grade his students papers presented with active HHV6 and cytomegalovirus infections and low NK cell functioning and VO2 max. He was able to return to work after 24 weeks of bi-weekly infusions. His VO2 max increased 47%, his NK function test went up 20% and he tested negative for both viruses. He had had ME/CFS for five years.
  • The third patient had classic, acute onset ME/CFS which progressed to seizures. Both serum and cerebral spinal fluid tested positive for HHV6. At the end of the Cifodovir trial the  viral load in his cerebral spinal fluid dropped from 3670 copies/ml to undetectable levels. Serum HHV6 was dramatically reduced (47,000 copies/ml to 3,000 copies/ml). Still symptomatic and experiencing cognitive problems, he was nonetheless able to return to work.


The retrospective study indicated Vistide (cifodovir) can have dramatic effects on functional capacity in HHV6 and/or HCMV infected ME/CFS patients.

Increasing VO2 max appeared to be critical to increasing functionality as the partial responders did not increase their VO2 max while on Cifodovir. At the FDA Advisory Meeting for Ampligen Dr. Bateman noted that VO2 max test results probably were, given the exertional problems in ME/CFS, the most difficult to ‘move’ test result in this disorder.

VO2 max levels in Dr. Peterson’s patients prior to Vistide administration were exceedingly low; they appeared to in the ‘very low’ range even for people for 65 years of age and older. Vistide moved those test results about 20% on average; leaving them still, it appeared, below normal but sufficient enough for a significant increase in functionality.

A Vistide Example

Vistide_CFSThe VO2 max tests suggested most patients had not returned to full health and Dr. Peterson has said he knows of few complete recoveries. I interviewed a former patient of Dr. Peterson’s several years ago. Faced with the loss of his career and the ability to care financially for his family Vistide turned out to be a godsend.

Cut down by acute onset ME/CFS, his VO2 max score topped out at an unbelievably low 15 (which qualified him for heart disease) and he was a ‘2’ out of 10 on his own energy scale (had trouble sitting up to eat).  Within a month on Vistide he was at a ‘4’; the next month he was a ‘5’ and sleeping soundly for the first time since he’d gotten sick. The next month he was a ‘7’ and his VO2 max tests had doubled to 28; still far below the 44 expected at his age, but an amazing increase, never the less.  Three months later he was at ‘90%’, back at work and able to do everything except exercise.

CMX001 – The Future Vistide? 

Dr. Peterson didn’t report on CMX001 in Paris, but sitting in the background of all this is a analogue of Vistide called CMX001 which appears to be a safer and more effective,  if not yet available, version of it. A  2012 review named CMX001 as one the ‘ten hot topics’ in antiviral research.

Chimerix Pharmaceuticals modified Vistide so that it can easily be taken up into the  tissues. That means no need for infusions, no worries about kidney problem and according to Chimerix, dramatically increased effectiveness.

CMX001 has been in development for  some time but just this March the FDA awarded the drug ‘fast track’ status for the prevention of cytomegalovirus infection.  Phase II trials are finished  and Phase III trials will get underway this year.

Given Dr. Peterson’s success with Vistide, FDA approval of CMX001 could be very good news for ME/CFS patients with HHV6, HCMV and/or possibly EBV infections.

Wrap Up

In a retrospective study Vistide proved to be  effective  in treating severely ill ME/CFS patients with HHV6 and HCMV infections. Dr. Peterson called for double-blinded, placebo-controlled studies to further study Vistide’s efficacy and mechanism of effect.  The CFI’s pathogen discovery studies due out this year should shed light on what percentage of ME/CFS patients could benefit from Vistide.

A Vistide analogue under development called CMX001 which does not require infusions and does not effect the kidneys could be boon for ME/CFS patients with herpesvirus infections if it is approved by the FDA. CMX001 was given fast-track status by the FDA earlier this year.


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  • Sarah Robinson

    April 9, 2013 at 6:01 pm - Reply

    What great news! Thank you, Dr. Peterson, for your diligence all these years in treating and studying ME/CFS patients. And thank you, Cort, for such competent coverage of this big news.

    • Cort Johnson

      April 9, 2013 at 6:10 pm - Reply

      Thanks Sara, this does strike as something very different; an antiviral we don’t hear about much which works very well in severely ill patients. I imagine, and I’m just guessing, that Vistide is probably the last drug of choice given the need for infusions. etc. and that anybody in this trial was probably really ill and had probably tried everything. If that’s true, the results are all the more appealing.

      I hope the FDA takes note! It’s a shame Dr. Peterson won’t be there to discuss the results of Vistide with them.

      • Jim

        May 16, 2014 at 5:47 am - Reply

        Does anybody know what specific test is used to determine “viral load” in Dr. Peterson’s work with Cidofovir… I am about to start treatment and would like to get this tested ASAP. Thanks!

        • Jim

          May 16, 2014 at 6:00 am - Reply

          Also, could somebody explain to me the significance of these results? I know they are positive but by how much? How do I interpret these tests?

          Chlamydia pneumoniae IgG 1:512
          EBV Anti-diffuse 1:40
          HHV-6 IgG 7.57
          HSV I/II IgG 45.7
          HSV, IgM I/II Combination 1.39
          M. pneumoniae 335 U/mL

  • Michael Murphy

    April 9, 2013 at 7:00 pm - Reply

    This is wonderful news, My best to Dr. Peterson and to Cort for bringing us this news. This fits my profile exactly. I have never had a spinal tap but I know this stuff is in my spinal fluid because of all the spinal pain I have. This is indeed great news for the ME World.

  • Questus

    April 9, 2013 at 10:55 pm - Reply

    This is interesting information.

    A missing piece of the equation for me is that it does not immediately appear to apply to patients who have been ill for decades.

    His examples include a patient who had been ill for 3 years, and one for five years. I’d be interested to know if he had success with any patients who have been debilitated for decades.

    I have 4 to 6 times the ‘normal’ viral load to CMV, HHV6, and EBV, so it’s very interesting to me.

    Well recall hearing Dr Cheney tell me once that the longer someone is ill with CFS, the longer they will continue to be sick.

    Cort, any information on how Vistide impacted patients who have been ill for decades?


    • Cort Johnson

      April 9, 2013 at 10:59 pm - Reply

      I noticed that as well Questus. Without knowing my guess is that Dr. Peterson is focusing on males to draw attention to the fact that males too, as we both know too well, also get this disorder, and they just happened to be ‘short-timers’. I would be surprised if it did not apply to people who had been ill for a long time as well but I don’t know. The interview I did with the guy that recovered enough to go back to work was with someone who’d had the disorder for a fairly short time as well.

      Good question…let’s see if we can get some more info…

      Really high loads of herpesviruses Questus! I imagine you fit this profile really well. It would be great if CMX001 breaks through to the marketplace in the near future. That could be good in several ways.

      It was interesting to see one person who recovered enough to go back to work still had quite low NK cell levels. I’ve also seen patients who raised their NK cell levels who didn’t improve (and I’m just the opposite response is seen) but it seems that getting rid of those viruses is the key..

    • Cort Johnson

      April 9, 2013 at 11:17 pm - Reply

      One question I had is how effective Vistide or CMX001 is against Epstein-Barr virus. The person I interviewed who was able to return to work had active levels of EBV, HHV6 and I think HCMV. This retrospective study, on the other hand, focused on HHV6 and HCMV.

      Does that mean Vistide is not effective against EBV? My guess is that it is but that other less difficult drugs are available to treat it. An study in Nature suggested it’s effective against EBV as well.

      Chimerix reports that CMX001 is not only effective against herpesviruses but against adenoviruses, small pox and others. It’s purportedly a more effective form of Vistide.

      • Sasha

        April 10, 2013 at 11:51 am - Reply

        Is there any sense of timescale for CMX001 being (a) approved for anything and (b) being available for PWME with high viral titres?

        • Cort Johnson

          April 10, 2013 at 1:45 pm - Reply

          I’m going to ask….

    • RW

      April 12, 2013 at 12:43 am - Reply

      Hello, I had CFS 19 years when Dr. Peterson prescribed Vistide. I had very good response to drug. I didn’t return to work- CFS too severe. Please see more , below.

  • Cort Johnson

    April 9, 2013 at 11:05 pm - Reply

    Some Facebook responses:

    Diane – That is good news!

    Jill Neimark Really good news–but I have a question. What do you mean by “tested positive”? Almost everybody has been exposted to EBV, for example, and HHV6 is common, too. I think you mean antibody level was high enough to indicate an active infection.
    about an hour ago · Like · 1

    Cort Johnson Yes, they were tested by PCR or antibody levels and something else and the levels of active virus either dropped enormously or were undetectable. Sometimes NK cells levels increased and VO2 max levels did somewhat but it was the disappearance of the viruses that seemed to be the key factor in the three cases Dr. Peterson pointed out.

  • Questus

    April 9, 2013 at 11:50 pm - Reply

    I’ve also seen patients who raised their NK cell levels who didn’t improve (and I’m just the opposite response is seen) but it seems that getting rid of those viruses is the key..

    Cort, are you saying you were able to raise your NK levels? How did you go about doing that.

    Think I would be a candidate for this protocol, but Dr. Klimas did not pursue antivirals for me immediately as I have a ‘profound leukopenia’ (low white cells). Not saying she would not go there eventually, but it was not her first choice.

    Cort, am interested in how you increased your NK count and? function. Am also interested in learning what other criteria Peterson’s patients had to have to fit his protocol.

    The article is excellent, but it sounds like all of us who are very ill and have high viral loads, and low NK count and function might qualify. Do you have a way of determining what other criteria Dr. Peterson is using to qualify patients for this study?

    Thanks for you work on this!


  • Cort Johnson

    April 10, 2013 at 12:12 am - Reply

    Sorry to give a false impression; I actually don’t think I’ve ever had NK cell functioning tested… I know that Corinne’s NK cell levels went up and she got better and then relapsed and she knows some patients with NK cell improvements who have not improved significantly. Its clear that NK cells are involved..Dr. Kogelnik noted the incredibly low levels he sees but they are obviously not the whole story…

    The presentation, unfortunatel, did not state what antibody or PCR levels were necessary to have a positive HHV6 or HCMV result.

  • Questus

    April 10, 2013 at 12:48 am - Reply

    Cort, I misunderstood you. Thought you had an improvement in NK function or quantity.

    Not sure who Corrine is, but how did she increase her NK cell level and function.

    NK cell testing includes both number of NK cells and how well those cells function, so 2 cofactors.

    Don’t all major CFS doctors agree that low NK function and levels are a hallmark of CFS?

    Am not sure what you mean by what it takes to determine HHV6 or CMV levels? It’s a common test. Mine were tested by both U of M by Dr. K but also by Quest labs.

    Perhaps I’m misunderstanding you.


    • Cort Johnson

      April 10, 2013 at 1:57 pm - Reply

      Corinne has been blogging on her experiences with Dr. Peterson. I’m not sure what did it but she was taking IVIV, procrit, IV Saline, IV amino acids, prescription probiotic and ?????.

      I would guess that all major ME/CFS doctors agreement on NK dysfunctionality; I would be surprised if they didn’t – t is consistently low in ME/CFS studies which suggests many people with ME/CFS demonstrate it but I don’t know what the percentage is. My guess is that they don’t all do NK cytoxicity tests nor do they require their patients to have low NKCC results which I believe Dr. Peterson does.

      I think you’re probably right about HHV6 and HCMV, I think its EBV where the controversy occurs although I’ll have to check. Kristin Loomis of the HHV6 foundation does believe HHV6 occurs in forms or places in the body that make it difficult to pick up in blood tests.

      • Joy

        April 17, 2013 at 4:13 pm - Reply

        My Natural Killer Cells tested very low while I had flu and an EBV re-activation, but then an immunologist said aspirin causes a false low and to do the test again after having no aspirin for 10 days. The 2nd test was normal. I wonder if all know about the need to have patients avoid aspirin products before these tests.

  • Els Van Hoof

    April 10, 2013 at 10:46 am - Reply

    I’ve been studying all different antiviral therapies against HHV6 for awhile..
    I’m positive for HHV6 PCR DNA test of my duodenum/stomach tissue.
    I’m also (highly) positive for EBV (EBNA) and CMV IgG in bloodsamples taken over an 11 year period (up to 11 fold maximum values).

    What I understood so far is that Cidofavir, Foscarnet and Valganciclovir are the top 3 of antiviral HHV6 medication according to in vitro and patient studies.

    The bad side of those antivirals are their side-effects (nepthrotoxic or bone marrow suppresive).
    Cidofavir being the least toxic of the three.

    The advantage of CMX001 would be
    – its low toxicity
    – it can cross the BBB; It enters the cells more easily than cidofavir.

    “This augmentation gives it a nearly 100-fold advantage over CDV in the in vitro inhibition of HHV6 allowing it to be effective at sub-cytotoxic concentrations”.

    But untill it’s approved cidofavir would be the best choice for HHV6 …

    I started with aciclovir high dosage together with Immunovir.
    I’m on it for about 3 months now but without any results (not bad, not bood … nothing changes).
    On my next visit I will ask about cidofavir. Which would be the best option at the moment I guess …
    Or else wait for CMX001 but that can still take years before it’s on the market.

    Thanx for the info Cort.

    • Cort Johnson

      April 10, 2013 at 2:08 pm - Reply

      It sounds like you, too, Else fit this profile very well. Thanks for the info on the HHV6 drugs; it sounds like it takes alot to get rid of the bug. I’ve sent an email to Chimerix to see if I can find out their timeline. Good luck!

    • VL

      April 11, 2013 at 5:03 am - Reply

      Hi Els, could you possibly tell us whether your doctor is indeed Dr Peterson? That may sound dumb but without your saying it I couldn’t be 100% sure. If so, could you possibly tell us whether the recent recall of vistide has affected you or other patients? I called up Gilead today and they reiterated that since Feb. they have not been able to supply vistide to any doctor (obviously Dr P looks like an exception, or the vistide he is giving was obtained before the recall). This is the FDA alert:

  • BC

    April 10, 2013 at 8:07 pm - Reply

    Thanks for this great article (and great news), Cort. Has this study been published ? If so, I would love the info..

    • Cort Johnson

      April 10, 2013 at 9:16 pm - Reply

      Right now its a conference presentation. Hopefully it’ll get published in a journal soon. I wonder what kind of reception it got in Paris….

  • VL

    April 11, 2013 at 5:16 am - Reply

    Hi Cort,

    Thanks so much for this report. Hope this isn’t repetitive but given that Dr P presented this just days ago do you know whether his treatment of his patients with Vistide (the patients that he has **now**) is affected by the Gilead recall? Not only did Gilead tell me that they have had no Vistide on their shelves since Feb., they also refused to commit to a statement that they would resume making it in the future. This tells me that they are covering for the possibility that they might NOT make it any more in the future. Do you know if Dr Peterson has said anything about this or how it might affect the availability of Vistide worldwide (since the recall is global)? Thank you so much.

  • RW

    April 12, 2013 at 12:23 am - Reply

    Excellent to see Vistide presented here. I was one of the 70%. CFS symptoms were affected too. All for the better, most notable was reduced fog and less painful crashing. Recovery time unaffected. Benefits continue 6 years later, unlike fragile experience with Ampligen. I have long term & severe CFS.

    • Cort Johnson

      April 12, 2013 at 2:52 am - Reply

      Thanks for letting us know about your experiences. Hopefully you’ll get a chance to see if CMX001 completes the job at some point.

    • VL

      April 14, 2013 at 6:11 am - Reply

      Hi RW,

      Would you be so kind as to tell us a) how much Vistide improved you by (%??), b) how long you were on vistide for and c) what factors helped you decide to stop–whether they were financial or say effects on renal function? Thanks so much.

  • Lisa Petrison, Ph.D.

    May 31, 2013 at 2:57 pm - Reply

    I have been hearing about the Vistide trial for a while and am glad to see Dr. Peterson release the results.

    I had a chance a while back to discuss Vistide with one of Peterson’s patients who had used it. This person said that while he thought that Vistide had been a little helpful, focusing on addressing toxic mold in the living environment had been significantly additionally helpful.

    This person had had CFS for many years and (after learning about the mold connection from me) suspected mold in the living environment. Rather than pursue extreme avoidance, this individual just moved to a different home, threw out all possessions that could not be washed and washed the rest. This person reported “at least a 20% improvement in the first few months and since then maybe another 15% improvement” — attributing all of this to the move.

    Note that this person is very complimentary of Peterson’s level of care. I think myself that he is an excellent physician and am grateful to him for his many years of service to CFS patients. Nonetheless, I think it is time for him to start focusing more of his attention on mold toxicity and proactively discussing it with his patients.

    (By the way, reports on whether people can be around their washed possessions after moving from a bad place vary from person to person. Some people succeed, others say absolutely not. It could be that some people are more reactive than others or reactive to different things, but I tend to think that it’s more that some toxins are much more damaging and harder to wash off than others. So YMMV.)

    For those unfamiliar with the health effects of mycotoxins, here is a citation list of peer-reviewed literature on the topic.

    Thanks for an interesting blog report, Cort.


    Lisa Petrison, Ph.D.
    lisapetrison at yahoo

    • Aidan Walsh

      June 21, 2014 at 6:40 pm - Reply

      True toxins such as radiation are impossible to wash off and one cannot get away from radiation it is even in rain drops. The truth will come out, not continued lies. A co-hort recently tested all have radiation.

  • Dale

    October 20, 2013 at 8:02 am - Reply

    I would give anything to try this as I have suffered since I was 8 or 10 yrs. old & now 67 yrs. old & progressing yrly. with the severe & debilitating exhaustion as my most difficult symptom. Fog would be next, but also have quite severe pain too. I have all the viruses mentioned in the beginning. My dr. does too, but she isn’t ill & says they have nothing to do with this condition. I believe they have everything to do with it, but wonder why she is fine & I am so terribly ill. Let’s hope help is coming soon for all of us. If I could donate my body now to science, I would. 😉

  • Aidan Walsh

    June 21, 2014 at 6:36 pm - Reply

    In the end when the full truth is told will we learn it is radiation sickness all along, even with the link on systemic mastocytosis/mast cell ‘activation’ disorders the cause of this I have no doubts will be radiation injuries. These Governments are is very serious trouble and lengthly jail terms will come.