Abstract: Understanding prions and the implications of iatrogenic Alzheimer’s disease
John Collinge, CBE, FRS, FMedSci, Director, MRC Prion Unit at UC London, Institute of Prion Diseases, London, England
Biography: John Collinge is Professor of Neurology and Head of the Department of Neurodegenerative Disease at the UCL Institute of Neurology and Director of the UK Medical Research Council (MRC) Prion Unit in London. He also directs the NHS National Prion Clinic at the adjacent National Hospital for Neurology and Neurosurgery. Professor Collinge trained in medicine at the University of Bristol and in neurology at St Mary’s Hospital and the National Hospital for Neurology and Neurosurgery in London. He is committed to highly multidisciplinary research and the seamless integration of basic laboratory and clinical research. He established the MRC Prion Unit at Imperial College London in 1998 where he held the positions of Wellcome Senior Clinical Fellow and then Wellcome Principal Clinical Fellow. His laboratory demonstrated in 1996 that the new human prion disease, variant CJD, was caused by the same prion strain as that causing BSE in cattle and has been responsible for a number of key advances in the field. Professor Collinge has served on numerous Government advisory committees on prion disease at a national, European Union and international level. He is committed to public communication of the Unit’s research and gives many media interviews. He is a Fellow of the Royal College of Physicians, a Fellow of the Royal College of Pathologists, a Founder Fellow of the UK Academy of Medical Sciences and a Fellow of the Royal Society. He was awarded a CBE for services to medical research by HM the Queen. He was also elected an Honorary Fellow of the American Neurological Association.
Abstract: Understanding prions and the implications of iatrogenic Alzheimer’s disease
Human prion diseases were thought unique in having an aetiological triad of inherited, sporadic and acquired forms. The recent ex vivo purification of prions to homogeneity and their structural determination at near atomic resolution by cryogenic electron microscopy confirmed that they comprise amyloid fibrillar assemblies of misfolded cellular prion protein and established the structural basis of prion strain diversity – how protein-only pathogens encode distinct phenotypes. While biophysically, all amyloid by definition can seed its own propagation, not all amyloids can act as an efficient pathogen that can invade and colonise a host, evade its natural defence mechanisms and cause lethal toxicity. Experimental transmissibility of amyloid-beta and other protein assemblies seen in the commoner neurodegenerative diseases is well established in animal models but its relevance for human disease remained controversial. The recognition of human transmission of amyloid-beta pathology from cadaver-derived pituitary growth hormone treatment and neurosurgical dura mater grafting (causing iatrogenic cerebral amyloid angiopathy, iCAA) and now iatrogenic Alzheimer’s disease (iAD) has changed this perspective. That AD (like amyloid-beta CAA) has the full triad of aetiologies characteristic of conventional prion diseases indicates that the principles of prion biology and therapeutic strategies for prion disease have relevance for other neurodegenerative diseases involving the accumulation of diverse assemblies of misfolded host proteins. In addition to important public health considerations to minimise future iatrogenic transmission of amyloid-beta and other proteopathic seeds, this should now allow broader insights from prion biology to be applied to AD and other neurodegenerative diseases.
https://secure.qgiv.com/event/mechanismsprionadrdconference/page/2208227/
Conference: Mechanisms of Neurodegeneration in Human Prion Diseases and Their Intersection with AD/ADRD
November 12 - 14, 2024
https://secure.qgiv.com/event/mechanismsprionadrdconference/page/2208227/
MONDAY, SEPTEMBER 11, 2023
Professor John Collinge on tackling prion diseases
“The best-known human prion disease is sporadic Creutzfeldt-Jakob disease (sCJD), a rapidly progressive dementia which accounts for around 1 in 5000 deaths worldwide.”
There is accumulating evidence also for iatrogenic AD. Understanding prion biology, and in particular how propagation of prions leads to neurodegeneration, is therefore of central research importance in medicine.
https://creutzfeldt-jakob-disease.blogspot.com/2023/09/professor-john-collinge-on-tackling.html
***> Singeltary Reply
Published: 09 September 2015
Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy
https://www.nature.com/articles/nature15369#article-comments
https://www.nature.com/articles/nature15369
Singeltary Comment at very bottom of this Nature publishing;
re-Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy
I would kindly like to comment on the Nature Paper, the Lancet reply, and the newspaper articles.
First, I applaud Nature, the Scientist and Authors of the Nature paper, for bringing this important finding to the attention of the public domain, and the media for printing said findings.
Secondly, it seems once again, politics is getting in the way possibly of more important Transmissible Spongiform Encephalopathy TSE Prion scientific findings. findings that could have great implications for human health, and great implications for the medical surgical arena. but apparently, the government peer review process, of the peer review science, tries to intervene again to water down said disturbing findings.
where have we all heard this before? it's been well documented via the BSE Inquiry. have they not learned a lesson from the last time?
we have seen this time and time again in England (and other Country's) with the BSE mad cow TSE Prion debacle.
That 'anonymous' Lancet editorial was disgraceful. The editor, Dick Horton is not a scientist.
The pituitary cadavers were very likely elderly and among them some were on their way to CJD or Alzheimer's. Not a bit unusual. Then the recipients ?
who got pooled extracts injected from thousands of cadavers ? were 100% certain to have been injected with both seeds. No surprise that they got both diseases going after thirty year incubations.
That the UK has a "system in place to assist science journalists" to squash embargoed science reports they find 'alarming' is pathetic.
Sounds like the journalists had it right in the first place: 'Alzheimer's may be a transmissible infection' in The Independent to 'You can catch Alzheimer's' in The Daily Mirror or 'Alzheimer's bombshell' in The Daily Express
if not for the journalist, the layperson would not know about these important findings.
where would we be today with sound science, from where we were 30 years ago, if not for the cloak of secrecy and save the industry at all cost mentality?
when you have a peer review system for science, from which a government constantly circumvents, then you have a problem with science, and humans die.
to date, as far as documented body bag count, with all TSE prion named to date, that count is still relatively low (one was too many in my case, Mom hvCJD), however that changes drastically once the TSE Prion link is made with Alzheimer's, the price of poker goes up drastically.
so, who makes that final decision, and how many more decades do we have to wait?
the iatrogenic mode of transmission of TSE prion, the many routes there from, load factor, threshold from said load factor to sub-clinical disease, to clinical disease, to death, much time is there to spread a TSE Prion to anywhere, but whom, by whom, and when, do we make that final decision to do something about it globally? how many documented body bags does it take? how many more decades do we wait? how many names can we make up for one disease, TSE prion?
Professor Collinge et al, and others, have had troubles in the past with the Government meddling in scientific findings, that might in some way involve industry, never mind human and or animal health.
FOR any government to continue to circumvent science for monetary gain, fear factor, or any reason, shame, shame on you.
in my opinion, it's one of the reasons we are at where we are at to date, with regards to the TSE Prion disease science i.e. money, industry, politics, then comes science, in that order.
greed, corporate, lobbyist there from, and government, must be removed from the peer review process of sound science, it's bad enough having them in the pharmaceutical aspect of healthcare policy making, in my opinion.
my mother died from confirmed hvCJD, and her brother (my uncle) Alzheimer's of some type (no autopsy?). just made a promise, never forget, and never let them forget, before I do.
I kindly wish to remind the public of the past, and a possible future we all hopes never happens again. ...
[9. Whilst this matter is not at the moment directly concerned with the iatrogenic CJD cases from hgH, there remains a possibility of litigation here, and this presents an added complication. There are also results to be made available shortly (1) concerning a farmer with CJD who had BSE animals, (2) on the possible transmissibility of Alzheimer's and (3) a CMO letter on prevention of iatrogenic CJD transmission in neurosurgery, all of which will serve to increase media interest.]
https://www.nature.com/articles/nature15369
Singeltary Comment at very bottom of this Nature publishing, takes a while to load...terry
https://www.nature.com/articles/nature15369#article-comments
Re-Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy
>>> The only tenable public line will be that "more research is required’’ <<<
>>> possibility on a transmissible prion remains open<<<
O.K., so it’s about 23 years later, so somebody please tell me, when is "more research is required’’ enough time for evaluation ?
Re-Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy
Nature 525, 247?250 (10 September 2015) doi:10.1038/nature15369 Received 26 April 2015 Accepted 14 August 2015 Published online 09 September 2015 Updated online 11 September 2015 Erratum (October, 2015)
snip...see full Singeltary Nature comment here;
Alzheimer's disease
let's not forget the elephant in the room. curing Alzheimer's would be a great and wonderful thing, but for starters, why not start with the obvious, lets prove the cause or causes, and then start to stop that. think iatrogenic, friendly fire, or the pass it forward mode of transmission. think medical, surgical, dental, tissue, blood, related transmission. think transmissible spongiform encephalopathy aka tse prion disease aka mad cow type disease...
Commentary: Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy
Alzheimer’s disease and Transmissible Spongiform Encephalopathy prion disease, Iatrogenic, what if ?
Posted by flounder on 05 Nov 2014 at 21:27 GMT
Alzheimer’s disease and Transmissible Spongiform Encephalopathy prion disease, Iatrogenic, what if ?
Background
Alzheimer’s disease and Transmissible Spongiform Encephalopathy disease have both been around a long time, and was discovered in or around the same time frame, early 1900’s. Both diseases are incurable and debilitating brain disease, that are in the end, 100% fatal, with the incubation/clinical period of the Alzheimer’s disease being longer (most of the time) than the TSE prion disease. Symptoms are very similar, and pathology is very similar.
Methods
Through years of research, as a layperson, of peer review journals, transmission studies, and observations of loved ones and friends that have died from both Alzheimer’s and the TSE prion disease i.e. Heidenhain Variant Creutzfelt Jakob Disease CJD.
Results
I propose that Alzheimer’s is a TSE disease of low dose, slow, and long incubation disease, and that Alzheimer’s is Transmissible, and is a threat to the public via the many Iatrogenic routes and sources. It was said long ago that the only thing that disputes this, is Alzheimer’s disease transmissibility, or the lack of. The likelihood of many victims of Alzheimer’s disease from the many different Iatrogenic routes and modes of transmission as with the TSE prion disease.
Conclusions
There should be a Global Congressional Science round table event set up immediately to address these concerns from the many potential routes and sources of the TSE prion disease, including Alzheimer’s disease, and a emergency global doctrine put into effect to help combat the spread of Alzheimer’s disease via the medical, surgical, dental, tissue, and blood arena’s. All human and animal TSE prion disease, including Alzheimer’s should be made reportable in every state, and Internationally, WITH NO age restrictions. Until a proven method of decontamination and autoclaving is proven, and put forth in use universally, in all hospitals and medical, surgical arena’s, or the TSE prion agent will continue to spread. IF we wait until science and corporate politicians wait until politics lets science _prove_ this once and for all, and set forth regulations there from, we will all be exposed to the TSE Prion agents, if that has not happened already.
end...tss
Alzheimer’s disease and Transmissible Spongiform Encephalopathy prion disease, Iatrogenic, what if ?
Posted by flounder on 05 Nov 2014 at 21:27 GMT
https://journals.plos.org/plosone/article/comment?id=10.1371/annotation/933cc83a-a384-45c3-b3b2-336882c30f9d
Ann N Y Acad Sci. 1982;396:131-43.
Alzheimer's disease and transmissible virus dementia (Creutzfeldt-Jakob disease).
Brown P, Salazar AM, Gibbs CJ Jr, Gajdusek DC.
Abstract
Ample justification exists on clinical, pathologic, and biologic grounds for considering a similar pathogenesis for AD and the spongiform virus encephalopathies. However, the crux of the comparison rests squarely on results of attempts to transmit AD to experimental animals, and these results have not as yet validated a common etiology. Investigations of the biologic similarities between AD and the spongiform virus encephalopathies proceed in several laboratories, and our own observation of inoculated animals will be continued in the hope that incubation periods for AD may be even longer than those of CJD.
https://pubmed.ncbi.nlm.nih.gov/6758661/
CJD1/9 0185 Ref: 1M51A
IN STRICT CONFIDENCE
Dr McGovern From: Dr A Wight Date: 5 January 1993 Copies: Dr Metters Dr Skinner Dr Pickles Dr Morris Mr Murray
TRANSMISSION OF ALZHEIMER-TYPE PLAQUES TO PRIMATES
1. CMO will wish to be aware that a meeting was held at DH yesterday, 4 January, to discuss the above findings. It was chaired by Professor Murray (Chairman of the MRC Co-ordinating Committee on Research in the Spongiform Encephalopathies in Man), and attended by relevant experts in the fields of Neurology, Neuropathology, molecular biology, amyloid biochemistry, and the spongiform encephalopathies, and by representatives of the MRC and AFRC. 2. Briefly, the meeting agreed that:
i) Dr Ridley et als findings of experimental induction of p amyloid in primates were valid, interesting and a significant advance in the understanding of neurodegenerative disorders;
ii) there were no immediate implications for the public health, and no further safeguards were thought to be necessary at present; and
iii) additional research was desirable, both epidemiological and at the molecular level. Possible avenues are being followed up by DH and the MRC, but the details will require further discussion. 93/01.05/4.1
http://web.archive.org/web/20090506012455/http://www.bseinquiry.gov.uk/files/yb/1993/01/05004001.pdf
BSE101/1 0136
IN CONFIDENCE
5 NOV 1992 CMO From: Dr J S Metters DCMO 4 November 1992
TRANSMISSION OF ALZHEIMER TYPE PLAQUES TO PRIMATES
1. Thank you for showing me Diana Dunstan's letter. I am glad that MRC have recognized the public sensitivity of these findings and intend to report them in their proper context. This hopefully will avoid misunderstanding and possible distortion by the media to portray the results as having more greater significance than the findings so far justify.
2. Using a highly unusual route of transmission (intra-cerebral injection) the researchers have demonstrated the transmission of a pathological process from two cases one of severe Alzheimer's disease the other of Gerstmann-Straussler disease to marmosets. However they have not demonstrated the transmission of either clinical condition as the "animals were behaving normally when killed'. As the report emphasizes the unanswered question is whether the disease condition would have revealed itself if the marmosets had lived longer. They are planning further research to see if the conditions, as opposed to the partial pathological process, is transmissible. What are the implications for public health?
3. The route of transmission is very specific and in the natural state of things highly unusual. However it could be argued that the results reveal a potential risk, in that brain tissue from these two patients has been shown to transmit a pathological process. Should therefore brain tissue from such cases be regarded as potentially infective? Pathologists, morticians, neuro surgeons and those assisting at neuro surgical procedures and others coming into contact with "raw" human brain tissue could in theory be at risk. However, on a priori grounds given the highly specific route of transmission in these experiments that risk must be negligible if the usual precautions for handling brain tissue are observed.
92/11.4/1-1 BSE101/1 0137
4. The other dimension to consider is the public reaction. To some extent the GSS case demonstrates little more than the transmission of BSE to a pig by intra-cerebral injection. If other prion diseases can be transmitted in this way it is little surprise that some pathological findings observed in GSS were also transmissible to a marmoset. But the transmission of features of Alzheimer's pathology is a different matter, given the much greater frequency of this disease and raises the unanswered question whether some cases are the result of a transmissible prion. The only tenable public line will be that "more research is required" before that hypothesis could be evaluated. The possibility on a transmissible prion remains open. In the meantime MRC needs carefully to consider the range and sequence of studies needed to follow through from the preliminary observations in these two cases. Not a particularly comfortable message, but until we know more about the causation of Alzheimer's disease the total reassurance is not practical.
JS METTERS Room 509 Richmond House Pager No: 081-884 3344 Callsign: DOH 832 121/YdeS 92/11.4/1.2
https://web.archive.org/web/20170126060344/http://collections.europarchive.org/tna/20080102232842/http://www.bseinquiry.gov.uk/files/yb/1992/11/04001001.pdf
''on the possible transmissibility of Alzheimer's''
9. Whilst this matter is not at the moment directly concerned with the iatrogenic CJD cases from hgH, there remains a possibility of litigation here, and this presents an added complication. There are also results to be made available shortly
(1) concerning a farmer with CJD who had BSE animals,
(2) on the possible transmissibility of Alzheimer's and
(3) a CMO letter on prevention of iatrogenic CJD transmission in neurosurgery, all of which will serve to increase media interest.
https://web.archive.org/web/20040315075058/http://www.bseinquiry.gov.uk/files/yb/1992/12/16005001.pdf
Alzheimer’s disease and Transmissible Spongiform Encephalopathy prion disease, Iatrogenic, what if ?
Posted by flounder on 05 Nov 2014 at 21:27 GMT
https://journals.plos.org/plosone/article/comment?id=10.1371/annotation/933cc83a-a384-45c3-b3b2-336882c30f9d
http://journals.plos.org/plosone/article/comments?id=10.1371/journal.pone.0111492
https://www.frontiersin.org/articles/10.3389/fnagi.2016.00005/full
THURSDAY, FEBRUARY 7, 2019
In Alzheimer's Mice, Decades-Old Human Cadaveric Pituitary Growth Hormone Samples Can Transmit and Seed Amyloid-Beta Pathology
https://betaamyloidcjd.blogspot.com/2019/02/in-alzheimers-mice-decades-old-human.html
Subject: CWD GSS TSE PRION SPINAL CORD, Confucius Ponders, What if?
REVIEW
***> In conclusion, sensory symptoms and loss of reflexes in Gerstmann-Sträussler-Scheinker syndrome can be explained by neuropathological changes in the spinal cord. We conclude that the sensory symptoms and loss of lower limb reflexes in Gerstmann-Sträussler-Scheinker syndrome is due to pathology in the caudal spinal cord. <***
***> The clinical and pathological presentation in macaques was mostly atypical, with a strong emphasis on spinal cord pathology.<***
***> The notion that CWD can be transmitted orally into both new-world and old-world non-human primates asks for a careful reevaluation of the zoonotic risk of CWD. <***
***> All animals have variable signs of prion neuropathology in spinal cords and brains and by supersensitive IHC, reaction was detected in spinal cord segments of all animals.<***
***> In particular the US data do not clearly exclude the possibility of human (sporadic or familial) TSE development due to consumption of venison. The Working Group thus recognizes a potential risk to consumers if a TSE would be present in European cervids.'' Scientific opinion on chronic wasting disease (II) <***
Saturday, February 2, 2019
CWD GSS TSE PRION SPINAL CORD, Confucius Ponders, What if?
https://familialcjdtseprion.blogspot.com/2019/02/cwd-gss-tse-prion-spinal-cord-confucius.html
Friday, January 29, 2016
Synucleinopathies: Past, Present and Future, iatrogenic, what if?
http://synucleinopathies.blogspot.com/2016/01/synucleinopathies-past-present-and.html
http://synucleinopathies.blogspot.com/
FRIDAY, JANUARY 10, 2014
vpspr, sgss, sffi, TSE, an iatrogenic by-product of gss, ffi, familial type prion disease, what it ???
Greetings Friends, Neighbors, and Colleagues,
vpspr, sgss, sffi, TSE, an iatrogenic by-product of gss, ffi, familial type prion disease, what it ???
Confucius is confused again.
I was just sitting and thinking about why there is no genetic link to some of these TSE prion sGSS, sFFi, and it’s really been working on my brain, and then it hit me today.
what if, vpspr, sgss, sffi, TSE prion disease, was a by-product from iatrogenic gss, ffi, familial type prion disease ???
it could explain the cases of no genetic link to the gss, ffi, familial type prion disease, to the family.
sporadic and familial is a red herring, in my opinion, and underestimation is spot on, due to the crude prehistoric diagnostic procedures and criteria and definition of a prion disease.
I say again, what if, iatrogenic, what if, with all these neurological disorders, with a common denominator that is increasingly showing up in the picture, called the prion.
I urge all scientist to come together here, with this as the utmost of importance about all these neurological disease that are increasingly showing up as a prion mechanism, to put on the front burners, the IATROGENIC aspect and the potential of transmission there from, with diseases/disease??? in question.
by definition, could they be a Transmissible Spongiform Encephalopathy TSE prion type disease, and if so, what are the iatrogenic chances of transmission?
this is very important, and should be at the forefront of research, and if proven, could be a monumental breakthrough in science and battle against the spreading of these disease/diseases.
the US National Library of Medicine National Institutes of Health pub-med site, a quick search of the word SPORADIC will give you a hit of 40,747. of those, there are a plethora of disease listed under sporadic. sporadic simply means (UNKNOWN).
http://www.ncbi.nlm.nih.gov/pubmed/?term=sporadic
the US National Library of Medicine National Institutes of Health pub-med site, a quick search of the word FAMILIAL will give you a hit of 921,815. of those, there are a plethora of disease listed under familial.
http://www.ncbi.nlm.nih.gov/pubmed/?term=familial
again, sporadic and familial is a red herring, in my opinion.
also, in my opinion, when you start have disease such as sporadic Fatal Familial Insomnia, (and or sporadic GSS, or the VPSPr type prion disease), and there is NO familial genetic linkage to the family of the diseased, I have serious questions there as to a familial type disease, and thus, being defined as such.
snip...see full text;
Friday, January 10, 2014
vpspr, sgss, sffi, TSE, an iatrogenic by-product of gss, ffi, familial type prion disease, what it ???
http://transmissiblespongiformencephalopathy.blogspot.com/2014/01/vpspr-sgss-sffi-tse-iatrogenic-by.html
22 years ago;
2001 Singeltary on CJD
February 14, 2001
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Terry S. Singeltary, Sr
Author Affiliations
JAMA. 2001;285(6):733-734. doi:10-1001/pubs.JAMA-ISSN-0098-7484-285-6-jlt0214
To the Editor: In their Research Letter, Dr Gibbons and colleagues1 reported that the annual US death rate due to Creutzfeldt-Jakob disease (CJD) has been stable since 1985. These estimates, however, are based only on reported cases, and do not include misdiagnosed or preclinical cases. It seems to me that misdiagnosis alone would drastically change these figures. An unknown number of persons with a diagnosis of Alzheimer disease in fact may have CJD, although only a small number of these patients receive the postmortem examination necessary to make this diagnosis. Furthermore, only a few states have made CJD reportable. Human and animal transmissible spongiform encephalopathies should be reportable nationwide and internationally.
https://jamanetwork.com/journals/jama/article-abstract/1031186
https://creutzfeldt-jakob-disease.blogspot.com/2023/09/professor-john-collinge-on-tackling.html
26 MARCH 2003
RE-Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States
Terry S. Singeltary, retired (medically)
I lost my mother to hvCJD (Heidenhain Variant CJD). I would like to comment on the CDC's attempts to monitor the occurrence of emerging forms of CJD. Asante, Collinge et al [1] have reported that BSE transmission to the 129-methionine genotype can lead to an alternate phenotype that is indistinguishable from type 2 PrPSc, the commonest sporadic CJD. However, CJD and all human TSEs are not reportable nationally. CJD and all human TSEs must be made reportable in every state and internationally. I hope that the CDC does not continue to expect us to still believe that the 85%+ of all CJD cases which are sporadic are all spontaneous, without route/source. We have many TSEs in the USA in both animal and man. CWD in deer/elk is spreading rapidly and CWD does transmit to mink, ferret, cattle, and squirrel monkey by intracerebral inoculation. With the known incubation periods in other TSEs, oral transmission studies of CWD may take much longer. Every victim/family of CJD/TSEs should be asked about route and source of this agent. To prolong this will only spread the agent and needlessly expose others. In light of the findings of Asante and Collinge et al, there should be drastic measures to safeguard the medical and surgical arena from sporadic CJDs and all human TSEs. I only ponder how many sporadic CJDs in the USA are type 2 PrPSc?
https://www.neurology.org/doi/10.1212/01.WNL.0000036913.87823.D6
Singeltary 2001
Subject: CJD or Alzheimer's or the same ???
Date: Sun, 29 Apr 2001 12:45:28 -0700
From: "Terry S. Singeltary Sr." Reply-To: Bovine Spongiform Encephalopathy
To: BSE-L@uni-karlsruhe.de
Bovine Spongiform Encephalopathy
Greetings List,
thought some might be interested in this. I have always wondered if CJD and or all TSEs and Alzheimer's could be linked. i have been of the opinion that Alzheimer's is a TSE for a long time, just at the low end of the titre of infectivity scale. i also believe in the accumulation theory. by dose, you could be killed by one sitting, or one injection, or one whatever, depending on the titre of infectivity of that whatever. on the other hand, if the dose is not a lethal dose, over a period of time, the accumulation will become lethal (if consumption continued), and i believe the route/source/titre of infectivity, will be a key roll to the incubation period, and symptoms.
just my opinion...terry
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