Severe immune response kills SARS victims

NewScientist.com news service ^ | May 3, 2003 | Robert Walgate

[CathyRyan]

An excessive immune reaction appears to be the fatal factor in patients who die of SARS, according to medical data from Hong Kong. The best estimate of the fatality rate of SARS is rising steadily and so understanding how the disease causes death is critical to finding the best treatments.

Scientists have also discovered that the SARS virus can remain viable for at least 24 hours after being deposited in a droplet on a plastic surface - a simulation, for example, of an infected person coughing on to the wall of a lift.

The new information was revealed by Klaus Stöhr, the World Health Organization's chief scientist for SARS in a briefing earlier this week. "In the first week or so of disease the virus is replicating mainly in the upper respiratory tract, causing high fever and dry cough. But in the second week we see an over-reaction of the immune response, and in 20 per cent of cases that leads to very severe disease."

Mark Salter, WHO's coordinator for the clinical management of SARS, told New Scientist that this excessive response seems to be destroying the alveoli, the tiny sacs at the end of the lung tubing where the oxygen is absorbed. It is like stripping all the leaves from a tree, he says, making breathing extremely difficult.

"The immune response develops, but then continues growing unchecked" says Salter. "You then get cytokines, tumour necrosis factor and so on released not just at the virally infected cells they are supposed to kill, but throughout the tissue". This also happens in other diseases but the mechanism is not entirely understood, and certainly not in the case of SARS, he says.

Flare up

Nevertheless the observation significantly strengthens the basis on which doctors can select the treatments given to patients. In particular, it suggests the use of corticosteroids, alongside other drugs that reduce the viral load such as interferon.

Corticosteroids suppress the immune system and are normally used against asthma, rheumatoid arthritis and in transplant patients to reduce the risk of rejection.

Their use does raise the risk of further infection, but Hong Kong hospitals are claiming success with combinations of the antiviral ribavirin and pulsed steroids, says Salter: "And once steroids are stopped, they see a flare up of the condition suggesting there is a significant immune component to the disease."

. The issue of how long the virus survives outside the body was also raised by Stöhr. Some scientists have argued that long survival could explain unusual cases of transmission in Hong Kong and Canada.

In a study in Germany reported by Stöhr, the virus was dropped in liquid on to a plastic surface, the drop was dried, and examined after 24 hours. "There were 10,000 virus units per millitre before, and after 24 hours there were 1000 - and that was viable viruses."

[SauronOfMordor]

Next week I'm supposed to go over to my business parter's place to take some digital pictures of her new products, so we can put it up on our web site. She's getting shipment of them in from China. I'm debating whether to show up in mask and gloves.

[vetvetdoug]

This SARS is more and more looking like a human form of the FIPV. Everything that has been discovered about SARS is parallel to the FIPV disease in cats. This has been scary from day one. The differences in symptoms, the difficulty in diagnosing the virus, the persistance now discovered, the infectiousness from fecal droplets and respiratory droplets, the immune response in respect to the severity of disease, and the scarring of the lungs,(etcetra ad nauseum) are all parallels.

[aristeides]

Illuminating article: Remaining calm in times of contagion. Especially this paragraph:

SARS is caused by a new type of coronavirus, which rapidly sabotages the human body's immune system and starts to reproduce. It makes inroads right into the lungs. It is not yet known whether the virus is extremely destructive during reproduction, or whether the body's immune system reacts so drastically to it that it damages the internal organs, causing breathing failure and even death.

[aristeides]

But a very low percentage of the present cat population comes down with FIP after infection. Of course, that may be because the fatal results of FIP have virtually eliminated the susceptible part of the population.

[vetvetdoug]

One thing about FR, one gets opinions and expertise from almost every profession known which in many cases explores the possibilities long before others get to those options. Some are good and some are bogus but that is what it takes to thoroughly study an entity. I am willing to bet that on some of these SARS threads the hypotheses that ultimately becomes fact exists.

[vetvetdoug]

That is because vets can test, isolate and put to sleep the animals with severe disease. Veterinarians have developed a competant vaccine to combat the disease in populations and have the experience of fighting the disease for several decades. Lets hope that in twenty years SARS is just a footnote in virology or genetics texts.

[blam]

"I am willing to bet that on some of these SARS threads the hypotheses that ultimately becomes fact exists."

I agree.

[Prince Charles]

In a study in Germany reported by Stöhr, the virus was dropped in liquid on to a plastic surface, the drop was dried, and examined after 24 hours. "There were 10,000 virus units per millitre before, and after 24 hours there were 1000 - and that was viable viruses."

While I haven't seen any info regarding the number of virus particles required to cause infection, it would seem that given the virulence of the Amoy Gardens outbreak, and the 10% viability after 24 hours, the required number must be low. More bad news.

[realpatriot71]

Excelent FYI on the Corona virus family, and some good info on SARS - with color pictures!

[EternalHope]

The Wall Street Journal could have gotten everything on your list from FreeRepublic a long time ago.

[EternalHope]

It maybe the biggest story in the world but is looks like it is starting to run out of steam on FR.

Don't know about you, but I feel like most of what there is to say right now has already been said. Sorta numb.

We seem to be entering a new phase. The biggest news right now is China. We all know it's out of control in China, but no one knows what's really going on there. That makes it hard to talk about.

[aristeides]

Interesting paragraph in your link:

Coronavirus infection is very common and occurs worldwide. The incidence of infection is strongly seasonal, with the greatest incidence in children in winter. Adult infections are less common. The number of coronavirus serotypes and the extent of antigenic variation is unknown. Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak.

[Domestic Church]

"Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak."

Nature's perfect culling machine.

[Domestic Church]

" Sorta numb."

Yep...recognizing the death sentence has been given.

[_Jim]

The topic of sars seems to be slowing. I wonder if people are getting burnt out on it?

Naw ... that's not it at all. There is an insatiable appetite for this sort of 'terror' in any public forum.

It COULD BE though, that the success in controlling and containing this cantagion as seen in several prominent corners of the world have taken the 'edge' off this as a pandemic though ...

[_Jim]

Lets hope that in twenty years SARS is just a footnote in virology or genetics texts.

One of the predictions I made weeks ago now: "The likely hood is that SARS will wind up being only being a footnote in medical history."

[_Jim]

the biggest story in the world

"Overblown appraisal"

[Domestic Church]

"Of course, that may be because the fatal results of FIP have virtually eliminated the susceptible part of the population."

That's exactly what is about to happen with SARS. Those of us genetically at risk will be wiped out.

[Domestic Church]

"Distribution of a genetic polymorphism (variant R131/H131 to be specific) of the Fcgamma receptor (CD32) may have implications for disease susceptibility if cirulating IgG2 is involved. It turns out that the spike glycoprotein of some coronaviruses might in fact have such activity.

The H131/R131 polymorphism is known to be an important outcome predictor in other diseases like bacterial respiratory infections, meningococcal infection, malaria, Dengue Hemorrhagic Fever, SLE, and Kaposi sarcoma. The H131 version has a high affinity for IgG2, while the R131 version of the receptor only binds IgG2 weakly.

More importantly, the H131 version is present in 61% of ethnic Chinese, 50% of Japanese, while only 23% of Caucasians or Asian Indians have the high affinity H131 CD32 receptor. "

[EternalHope]

There is an insatiable appetite for this sort of 'terror' in any public forum.

It COULD BE though, that the success in controlling and containing this cantagion as seen in several prominent corners of the world have taken the 'edge' off this as a pandemic though ...

Figured you'd be along eventually, and with a comment about like the one you made. Predictable, but helps stir things up, too. Reminds us all how deep that river in Egypt really is.

Everyone on this forum who is informed about SARS has been hoping for containment in the cities it has affected the most, and it looks like we may have gotten our wish.

It's too soon to be sure about Hong Kong. They changed their definition of a SARS case at the same time their numbers started getting better. Per loin has a very interesting graph that shows the result here: Graph of Hong Kong cases. I'm interested in your take on the Hong Kong numbers.

I'm also interested in your take on the situation in Beijing and the situation in China in general. Perhaps you could also comment on the Chinese government's announcement that a vaccine for SARS is "likely in the coming few months", and how that compares with the new Chinese diagnostic test for SARS they announced two weeks ago.

You have mentioned The People's Daily as one of your sources a couple of times in the past, so you might want to go here: People's Daily says SARS vaccine is coming. The article reassures the Chinese people that better treatment and a vaccine are coming soon.

All of us already know where you stand overall, and the "diplomatic" way you have of expressing yourself. However, the questions I asked were serious. I would truly like to see your take on this.

I can only Freep a few more minutes, but I'll check back this evening.