Ebola Transmissibility

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Re: WHO - What we know about transmission of the Ebola virus among humans - Oct 6 2014

Re: WHO - What we know about transmission of the Ebola virus among humans - Oct 6 2014

Translation: in theory we know how to stop Ebola but we are unable to respond at a large enough scale so send us more money.

The officials who are in charge have never had a sense of urgency about stopping this outbreak. I've seen countless examples like the ceremony for putting 5 donated ambulances in service that took everyone off duty for an afternoon, or the delays in cleaning the Texas apartment. We need results, not nice statements, we need a plan that can guarantee isolation of the virus as this is the only known way to stop it. Vaccinations are a long way off and there are more and more cases being exported from this region. Authorities need to take decisive action.

 

[sharon sanders]

Re: Ebola Transmissibility

This is the deal with the WHO - They can't do anything without permission of the member states. It is much more effective to direct attention to the respective states themselves.

 

[Pathfinder]

Re: Ebola Transmissibility

WHO

What we know about transmission of the Ebola virus among humans

Ebola situation assessment - 6 October 2014

The Ebola virus is transmitted among humans through close and direct physical contact with infected bodily fluids, the most infectious being blood, faeces and vomit.

The Ebola virus has also been detected in breast milk, urine and semen. In a convalescent male, the virus can persist in semen for at least 70 days; one study suggests persistence for more than 90 days.

Saliva and tears may also carry some risk. However, the studies implicating these additional bodily fluids were extremely limited in sample size and the science is inconclusive. In studies of saliva, the virus was found most frequently in patients at a severe stage of illness. The whole live virus has never been isolated from sweat.

The Ebola virus can also be transmitted indirectly, by contact with previously contaminated surfaces and objects. The risk of transmission from these surfaces is low and can be reduced even further by appropriate cleaning and disinfection procedures.
...
No evidence for mutation of this virus

Moreover, scientists are unaware of any virus that has dramatically changed its mode of transmission. For example, the H5N1 avian influenza virus, which has caused sporadic human cases since 1997, is now endemic in chickens and ducks in large parts of Asia.

That virus has probably circulated through many billions of birds for at least two decades. Its mode of transmission remains basically unchanged.

Speculation that Ebola virus disease might mutate into a form that could easily spread among humans through the air is just that: speculation, unsubstantiated by any evidence.

This kind of speculation is unfounded but understandable as health officials race to catch up with this fast-moving and rapidly evolving outbreak.

To stop this outbreak, more needs to be done to implement ? on a much larger scale ? well-known protective and preventive measures. Abundant evidence has documented their effectiveness.

WHO

This is one of the studies that WHO is referring to:

How does Ebola spread? Hard facts from key studies

By Kelly ServickJon Cohen
3 October 2014 3:00 am
...
A crucial 2007 paper, published in The Journal of Infectious Diseases, offers perhaps the best indication available of where the risks lie, and where they don?t. It analyzed samples from confirmed cases during a 2000 outbreak in Uganda, including people who were acutely ill or recovering. It also looked for the virus on objects, such as desks, walls, and gloves, in an Ebola isolation ward. The study?s numbers are small, but it?s the most detailed analysis published to date.
Below are the 2007 study?s key tables. One major takeaway: Infection is unlikely to come from a fateful encounter with a doorknob, or even from a handshake. The authors point out, however, that the methods they used to detect Ebola haven?t been extensively tested for use on objects, and the virus could have been present at undetectable concentrations.

<FIGURE class=newsimg>

...
http://news.sciencemag.org/africa/20...ts-key-studies


Concerning the mutation of the virus, according to Peter Piot:

"The virus is continually changing its genetic makeup. The more people who become infected, the greater the chance becomes that it will mutate ...

... which might speed its spread. Yes, that really is the apocalyptic scenario. Humans are actually just an accidental host for the virus, and not a good one. From the perspective of a virus, it isn't desirable for its host, within which the pathogen hopes to multiply, to die so quickly. It would be much better for the virus to allow us to stay alive longer.

Could the virus suddenly change itself such that it could be spread through the air?

Like measles, you mean? Luckily that is extremely unlikely. But a mutation that would allow Ebola patients to live a couple of weeks longer is certainly possible and would be advantageous for the virus. But that would allow Ebola patients to infect many, many more people than is currently the case.

But that is just speculation, isn't it?

Certainly. But it is just one of many possible ways the virus could change to spread itself more easily. And it is clear that the virus is mutating.

http://www.flutrackers.com/forum/showthread.php?t=228205

 

[Vibrant62]

Re: Ebola Transmissibility

On the basis of the above study, it would seem that virus is most prevalent in saliva. If so could this represent the primary transmission fluid, with stools as the second largest problem?

That would argue for a greater transmission risk in any situation where spittle might fly - kissing as well as coughing and sneezing via droplet transmission. Even standing too close to an infected person talking? Infected spittle landing on another person could easily reach hands and from there, mucous membranes if hands touch faces or rub eyes, even if it is less than likely to be inhaled.

 

[AlaskaDenise]

Re: Ebola Transmissibility

The phrase "no mutation for this virus" may be too general. Further in the article they explain it to mean no change in mode of transmission. There is however, considerable genetic variation between strains and it does mutate quickly.

Ebola virus mutating rapidly as it spreads

......The researchers sequenced the viral genomes from each sample an average of more than 2,000 times, allowing them track how the virus mutated as it spread from patient to patient.....

.....Further comparisons suggest that the virus that caused the outbreak separated from those that caused past Ebola outbreaks about 10 years ago. It had accumulated more than 395 mutations between that time and June, when the researchers collected the last samples included in today's analysis

...The virus amassed 50 mutations during its first month, the researchers found.....

.....Some changes have occurred in regions of the genome that are targeted by diagnostic tests. This does not mean the tests are ineffective, but confirming this and continuing to monitor such mutations will be crucial, Chiu says.

.

 

[AlaskaDenise]

Re: Ebola Transmissibility

We could speculate that the mutation rate is the virus adapting to a new host? But since it is so successful at spreading it doesn't have a "reason" to increase mode of transmission.

Reston Ebola was confined to non-human primates and even Phillipine workers involved in their collection never became ill, in spite of showing antibodies. However, in 2009 pigs in the Phillipines became sick with Reston ebola and transmitted it to humans! An interesting fact in the pig cases, is that they were co-infected with other porcine diseases - making them super-spreaders? Yet again, the humans never became ill but acquired antibodies.

First pig-to-human transmission of Ebola-Reston virus

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[Vibrant62]

Re: Ebola Transmissibility

I would argue that mankinds actions to contain ebola, if imperfect, would actually help speed mutation and adaptation.

To explain what I mean by this: if we are really good at contact tracing, isolation and control of close contacts after the infected have become symptomatic, then any mutation that permitted spread before the host became overtly symptomatic would be selected for (there is plenty of viral precedent for this e.g. flu, where people are at their most infectious just before onset of symptoms and in the first few days after infection). This variant would then transmit, and standard measures might pick up all the people infected post the primary case becoming symptomatic, but it would take some time before we realised that there were cases appearing in pre-symptomatic contacts i.e the old rules of 'infectious only when symptomatic' were no longer true i.e we would still be seeing spread but would not understand why. By todays measures, low risk contacts prior to a case becoming symptomatic probably wouldnt even be monitored.

Another example: very good contact tracing, isolation and control measures might provide evolutionary pressure for selection towards a variant where the incubation period to symptoms is small i.e 2 - 5 days. That would dramatically shorten the window to find people and isolate them before they spread the virus onwards. Isolation, containment and control would still work, but it would make it much harder, and would need to be much faster than at present.

In summary, there are many different ways ebola could be under pressure to adapt - those are just two examples, never mind the physiological adpatations that arise from a zoonosis becoming a human virus.

The key here is to be 100% efficient in contact tracing, make sure all possible contacts are identified and monitored from several days pre-symptoms emergence, i.e go 'overboard' to pick up any such outliers fast, so that any 'mutant' infections do not escape the net and allow a wider transmission chain to start.

 

[AlaskaDenise]

Re: Ebola Transmissibility

I would argue that mankinds actions to contain ebola, if imperfect, would actually help speed mutation and adaptation..........

The key here is to be 100% efficient in contact tracing, make sure all possible contacts are identified and monitored from several days pre-symptoms emergence, i.e go 'overboard' to pick up any such outliers fast, so that any 'mutant' infections do not escape the net and allow a wider transmission chain to start.

You have good points about which actions might speed mutation and adaptation. Although, this virus is capable of significant mutation while in hiding - between outbreaks.

Catching those "mutants" will probably require a trained STAT HCW force roughly equivalent to the allied forces of WW II. Costly, in many ways, but necessary.

.

 

[Vibrant62]

Re: Ebola Transmissibility

I am concerned that not enough weight is being given to the potential of fomite transmission in spread dynamics, both within hospital protocols (CDC) and when assessing risks of community spread via an infected individual.

If we look at what is occuring in west africa, I think that 'boots on the ground' are well aware of these risks, especially when you consider that the data shows that as few as 10 virions are required to produce an infection, if those virions reach a mucous membrane - easily done if infected hands touch face or eyes, which apparently we do numerous times each hour unconsciously. A single droplet of spittle could contain a million such virions.

Therefore, to provide some perspective, here is a good recent overview on what we know about fomite transmission. These findings should also apply to ebola, except that ebola has an infectivity equivalent to a respiratory virus i.e a very low number of virions reaching the right place i.e a mucosa are required to produce infection.

Significance of Fomites in the Spread of Respiratory and Enteric Viral Disease
http://aem.asm.org/content/73/6/1687.long

 

[JimO]

Re: Ebola Transmissibility

Ebola is often compared to flu and other repiratory diseases, but I have not seen a comparison with norovirus. The R0 for norovirus is about twice that of ebola, but the incubation period is shorter, so the result is that it can move through the population much more quickly. However, like ebola, I don't believe that transmission of norovirus has an airborne component (correct me if I'm wrong). If so, then what makes norovirus so contagious? Fomite transmission is certainly a major factor in spreading norovirus. It would be interesting to make a direct comparison between the two to see if the data suggests that fomite transmission plays a significant role in an ebola outbreak.

 

[Emily]

Re: Ebola Transmissibility

Noro involves explosive diarrhea and projectile vomiting. I'm not sure about ebola.

Noro is non-enveloped so harder to disinfect than an enveloped virus like ebola. (Maybe that is why the comparisons to flu in some aspects?)

Persistence? I'm not sure on noro, but below the persistence of ebola is estimated to range from minutes to hours depending on the surface by Gavin Macgregor-Skinner. I think he was involved in the successful Nigerian containment.

http://www.c-span.org/video/?321618-3/washington-journal-gavin-macgregorskinner-ebola-outbreak

(Note: I'm wondering about a still wet puddle or wadded up rag that is contaminated - could that stay infective longer than the surfaces Skinner is talking about?)

 

[Dani]

Re: Ebola Transmissibility

CIDRAP- WHO, CDC Dissect Ebola Transmission Risk

Still downplaying role of fomites.

 

[hereiam]

Re: Ebola Transmissibility

Ebola is often compared to flu and other repiratory diseases, but I have not seen a comparison with norovirus. The R0 for norovirus is about twice that of ebola, but the incubation period is shorter, so the result is that it can move through the population much more quickly. However, like ebola, I don't believe that transmission of norovirus has an airborne component (correct me if I'm wrong). If so, then what makes norovirus so contagious? Fomite transmission is certainly a major factor in spreading norovirus. It would be interesting to make a direct comparison between the two to see if the data suggests that fomite transmission plays a significant role in an ebola outbreak.

Hello all - I have been lurking here for 18+ (pre-ebola) months, and trying to register since August. I feel like I know all of you already, and here I am crashing the party and suddenly inserting myself into your conversations!

Jim, I want to know the answers to these questions too. We are told that aerosol to airborne transmission would be a big evolutionary leap. But would a leap to norovirus-level transmission be less so for ebola? Because norovirus infects 21 Million each year in the US alone.

As a mom I just think of all those times my kids got it and it swept through the whole household within days. Awful illness -- as anyone who's had it can attest. But we are all still alive. When I think about ebola going endemic, I think about this scenario, only more lethal.

 

[curiosity]

Re: Ebola Transmissibility

I think by the time it adapts well enough to a human host to be as contagious as norovirus, it will have passed through the entire world population once or twice in slower motion.

One thing Norovirus is good at is genetic change - and the host immunity does not stick around for long.

 

[curiosity]

Re: Ebola Transmissibility

On the other hand, maybe it IS as contagious as norovirus with a longer incubation period. The incubation period gives us the opportunity to contain it, the mortality rate gives us the reason. That being said, adaptability may mean shorter incubation periods and before you know it, you've got a cruise ship full of Ebola.

 

[MedStudent_18]

Re: Ebola Transmissibility

Both ebola and norovirus are single-stranded RNA viruses, but are different in several key areas.

• Ebola is a long, filamentous particle with a lipid envelope, thus making it highly susceptible to dessication. Norovirus is a small, naked, spheroid virus. Its lack of a lipid envelope makes this virus extremely persistant in the environment.
• Norovirus infects the small intestines, which causes the high viral titers seen in vomit and in stool. Ebola seems to prefer the blood stream. As long as an ebola patient doesn't slice their corotids in half, I can't see aerosol transmission being a major concern. That could change, however, if the selective pressure is there.
• Ebola takes too long to start up an infection. Compare its average incubation peroid of 8-10 days with norovirus's incubation peroid of 36-48 hours.
• The biggest difference I see is virulence. Ebola simply hits too hard and too sudden for its own good. Norovirus hits fast, and it may cause discomfort, but it keeps you around long enough to guarantee it gets passed to the next host.

Hope that helps.

 

[AlaskaDenise]

Re: Ebola Transmissibility

I believe Marburg is the closest pathogen to ebola. They are the apple to apple comparison.

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[AlaskaDenise]

Re: Ebola Transmissibility

I believe Marburg is the closest pathogen to ebola. They are the apple to apple comparison.

.

Good summary of the similarities:

What is Marburg, the Ebola-like virus that killed a health-care worker in Uganda?

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[Emily]

Re: Ebola Transmissibility

Both ebola and norovirus are single-stranded RNA viruses, but are different in several key areas.

• Ebola is a long, filamentous particle with a lipid envelope, thus making it highly susceptible to dessication. Norovirus is a small, naked, spheroid virus. Its lack of a lipid envelope makes this virus extremely persistant in the environment.
• Norovirus infects the small intestines, which causes the high viral titers seen in vomit and in stool. Ebola seems to prefer the blood stream. As long as an ebola patient doesn't slice their corotids in half, I can't see aerosol transmission being a major concern. That could change, however, if the selective pressure is there.
• Ebola takes too long to start up an infection. Compare its average incubation peroid of 8-10 days with norovirus's incubation peroid of 36-48 hours.
• The biggest difference I see is virulence. Ebola simply hits too hard and too sudden for its own good. Norovirus hits fast, and it may cause discomfort, but it keeps you around long enough to guarantee it gets passed to the next host.

Hope that helps.

Very helpful, thanks!

 

[JimO]

Re: Ebola Transmissibility

Both ebola and norovirus are single-stranded RNA viruses, but are different in several key areas.

• Ebola is a long, filamentous particle with a lipid envelope, thus making it highly susceptible to dessication. Norovirus is a small, naked, spheroid virus. Its lack of a lipid envelope makes this virus extremely persistant in the environment.
• Norovirus infects the small intestines, which causes the high viral titers seen in vomit and in stool. Ebola seems to prefer the blood stream. As long as an ebola patient doesn't slice their corotids in half, I can't see aerosol transmission being a major concern. That could change, however, if the selective pressure is there.
• Ebola takes too long to start up an infection. Compare its average incubation peroid of 8-10 days with norovirus's incubation peroid of 36-48 hours.
• The biggest difference I see is virulence. Ebola simply hits too hard and too sudden for its own good. Norovirus hits fast, and it may cause discomfort, but it keeps you around long enough to guarantee it gets passed to the next host.

Hope that helps.

Yes, thanks very much.