Up to half of Ebola infections may be asymptomatic and not infectious

Lifted from a FluTrackers thread:

www.flutrackers.com...

Asymptomatic seropositive cases are unlikely to be infectious, but they will nonetheless contribute to population immunity, thereby acting to decrease the rate of spread in way that's similar to vaccination. These cases may also be another source of serum for transfusion therapy.

Ebola control: effect of asymptomatic infection and acquired immunity

"Evidence suggests that many Ebola infections are asymptomatic, a factor overlooked by recent outbreak summaries and projections. Particularly, results from one post-Ebola outbreak serosurvey showed that 71% of seropositive individuals did not have the disease; another study reported that 46% of asymptomatic close contacts of patients with Ebola were seropositive. Although asymptomatic infections are unlikely to be infectious, they might confer protective immunity and thus have important epidemiological consequences."

Human asymptomatic Ebola infection and strong inflammatory response

"This study showed that asymptomatic, replicative Ebola infection can and does occur in human beings. The lack of genetic differences between symptomatic and asymptomatic individuals suggest that asymptomatic Ebola infection did not result from viral mutations. Elucidation of the factors related to the genesis of the strong inflammatory response occurring early during the infectious process in these asymptomatic individuals could increase our understanding of the disease."

As far as I understand in one study they found 71% of individuals who tested positive for Ebola antibodies never fell ill. 43% of those in close contact with infected, symptomatic individuals were found to be asymptomatic.

Great news? Or the worst news we've received yet?

Can somebody with a better jargon grasp interpret?

Basically, some folks get the virus but not the symptoms.
Then they have antibodies that give them immunity.

This is why testing is important.
A person who has developed antibodies but has no symptoms is still a case of ebola.
Knowing this information would help the study and eventual handling of the disease.
Also, study of these people would help develop ways to fight the disease.

This could be god awful if they can in fact be infectious.

It also raises questions for me about Duncan's family (see thread about their statement for skepticism, it seems to me falsified and not authored by Louise Troh) are they being held and tested/studied because they are the first confirmed asymptomatic carriers in the US? How many other people have unknowingly (asymptomatically) brought it to the states already?

a reply to: JG1993

It means you can be infected and not get sick. It means that because you are infected and don't get sick you will probably not transmit the disease because it is only transmissible when there are symptoms. It means that because of this there can be a natural "herd immunity" effect which slows the spread of the disease. It also means that the serum of those who are infected but don't get sick might be used to make a vaccine.

Somebody who already has an infection might already have an immune system on "high alert", so the immune system is more likely to go after anything foreign and thus kill the first few Ebola virus particles. It could just be luck or previous exposure to something similar in the past.

Herpes can be spread without symptoms, apparently.

Asymptomatic-infected people shed herpes virus only about half as often as do people who have herpes symptoms. But when they are shedding virus, they shed just as much as people who have frequent symptoms (unless they are having an active herpes outbreak).

Trying to find if any other viral infections do the same. I don't believe herpes and Ebola share much in common structurally/genetically. But the OP study doesn't claim that they have proved whether or not the asymptomatic Ebola carriers are infectious as far as I could read.

Ebola Reston,
The strain that was imported to the monkey facility in Reston Virginia back in the 80's was deadly to monkeys but the four humans that were infected with the virus had no symptoms.

The strain was almost exactly the same as ebola Zaire which is 90% lethal in humans. It was imported in crab eating macaque monkeys from the Philippines.

The strain was almost exactly the same as ebola Zaire which is 90% lethal in humans.

The study is about the "Zaire" variety, which is actually termed "ebola virus." It involved patients during the 1996 Gabon outbreak.

Of course, you chose the high end of the death rate. It varies. In 1996 Gabon it was 70%

originally posted by: Phage

The strain was almost exactly the same as ebola Zaire which is 90% lethal in humans.

The study is about the "Zaire" variety, which is actually termed "ebola virus." It involved patients during the 1996 Gabon outbreak.

Of course, you chose the high end of the death rate. It varies. In 1996 Gabon it was 70%

We're talking about different things.
I was pointing out that reston is an ebola strain that is not lethal to humans.
Reston was not a study. It was an outbreak in a facility in virginia. It repeatedly tested positive for Ebola Zaire but only killed monkeys.
It infected four humans who also tested positive for Ebola Zaire but had no symptoms.

And yes, I chose the higher rate of death simply to give you something to do.
I know how bored you can get.

a reply to: badgerprints

I was pointing out that reston is an ebola strain that is not lethal to humans.

So, it was an utter irrelevancy since it has nothing to do with the topic or the epidemic in West Africa.
Got it.

a reply to: badgerprints

Important points. ....Does seem to be the symptoms that spread the virus but why? Is it a 'vehicle of transmission" thing? What other factors might be important?

originally posted by: Phage
a reply to: badgerprints

I was pointing out that reston is an ebola strain that is not lethal to humans.

So, it was an utter irrelevancy since it has nothing to do with the topic or the epidemic in West Africa.
Got it.

No need to be obtuse.
It's a strain that is almost identical to the current strain but is asymptomatic in humans.
It's clearly possible that there is a link between an asymptomatic strain and a strain that has 40-70% asymptomatic infection.
The study of the difference between the two could show a key to a vaccine.

originally posted by: badgerprints
Ebola Reston,
The strain that was imported to the monkey facility in Reston Virginia back in the 80's was deadly to monkeys but the four humans that were infected with the virus had no symptoms.

The strain was almost exactly the same as ebola Zaire which is 90% lethal in humans. It was imported in crab eating macaque monkeys from the Philippines.

So are the people infected with the Reston Ebola healthy now? Or are they -still- carrying around the virus asymptomatically?

If they are still infected but are symptom-free, or they are not infected any longer and are Ebola-free now (either way works for Reston), they may be a good source of what the OP is stating.

Dr. Kent Brantly has overcome Ebola Zaire, and is giving blood donations to different people. I guess that means that he is considered completely healed at this point. i.e. not infecting others unintentionally.