# 369
It’s a sobering reality, but what we don’t know about the H5N1 virus, and how it might evolve into a pandemic, or how that virus would affect the human body if it does, could fill volumes. At every turn it seems, when writing on the subject, I’m forced to use some qualifier lest I lead my readers astray.
Part of the problem is that, despite our advanced technology and medical science, we don’t have the answers to a number of very basic questions.
I can’t tell you, with absolute certainty, if any of the following statements commonly heard are true or not.
The only `airborne’ transmission of influenza is through large droplets (IE. sneezing, coughing). You are relatively safe from infection beyond X number of feet.
The virus cannot survive on fomites (inanimate objects) for longer than 24-48 hours.
In order for a virus to become a pandemic the CFR (Case Fatality Ratio) must drop to a level closer to that seen in 1918 (2%).
The primary cause of death among Avian flu victims is ARDS, brought on by a `Cytokine Storm’.
There are few, if any, asymptomatic or `mild’ cases of H5N1 infection.
The next pandemic will be caused by the H5N1 virus.
Six relatively basic statements that I’ve seen bandied about on the Internet as if we know them as fact.
We don’t.
Most of these are assumptions, based on limited testing or anecdotal reporting; `Conventional wisdom’ that may, or many not be true.
Part of the problem has been that influenza has been so ubiquitous in our lives that it has received little attention. It has been perceived as a `nuisance illness’, despite its yearly toll on humanity, and has been neglected by researchers over the years.
The conventional wisdom for years has been that influenza is spread primarily through coughing and sneezing, via large droplets, and by touching contaminated objects (fomites) such as door handles and telephone receivers. Aerosolized spread of the disease has been largely ignored.
This assumption could have tragic consequences. The Canadian Pandemic Influenza Plan and the US Department of Health and Human Services Pandemic Influenza Plan both recommend surgical masks, not N95 masks, as part of personal protective equipment for routine patient care. These surgical masks would not provide the level of protection against an aerosolized virus that the N95 masks provide.
In November of 2006, the Journal of Emerging Infection Diseases published a review of the literature regarding the transmission of the influenza virus. Based on this review, they conclude:
Abstract
In theory, influenza viruses can be transmitted through aerosols, large droplets, or direct contact with secretions (or fomites). These 3 modes are not mutually exclusive. Published findings that support the occurrence of aerosol transmission were reviewed to assess the importance of this mode of transmission. Published evidence indicates that aerosol transmission of influenza can be an important mode of transmission, which has obvious implications for pandemic influenza planning and in particular for recommendations about the use of N95 respirators as part of personal protective equipment.
Compelling, but not conclusive. `In theory’ . . . `findings that support’ . . . `evidence indicates’ . . .
Even the experts aren’t 100% sure.
I’ve seen statements on how long the influenza virus can remain viable on fomites, inanimate objects, which range from 6 hours up to 7 days. It depends on the type of surface, temperatures, relative humidity, exposure to sunlight, and a variety of environmental factors. The best anyone can say is; it varies.
Up until a few months ago, the `conventional wisdom’ was that no pandemic could sustain itself with a high case fatality ratio. In order to propagate, it required living hosts, and a pathogen that was too efficient of a killer, would extinguish itself before spreading.
Governments around the world, using this bit of wisdom, have ignored the current apparent CFR of over 50% (in 2006 > 60%) of the H5N1 virus, and have planned for only a 2% fatality rate in a pandemic.
Last September, the WHO released a report where they admit the possibility that the CFR need not necessarily drop in a pandemic.
Should the virus improve its transmissibility by acquiring, through a reassortment event, internal human genes, then the lethality of the virus would most likely be reduced. However, should the virus improve its transmissibility through adaptation as a wholly avian virus, then the present high lethality could be maintained during a pandemic.
An important admission, but one that has gained little traction in government planning around the world.
As far as the cause of deaths from avian influenza, we have recently gained new insight on this by work done on the revived Spanish Flu virus by Canadian researchers. ARDS (Acute Respiratory Distress Syndrome) as a result of the long suspected `cytokine storm’ does appear to be a major factor, at least in that virus’s action on the human body.
But what we don’t know is how to control this immune response to a novel influenza virus, nor do we know much about how the H5N1 virus affects other organs of the body. Most of the fatalities, thus far, have been in developing nations where autopsies are rarely preformed due to cultural and religious views.
Once again, our direct knowledge is very limited.
The question of whether there are large numbers of asymptomatic, or `mild’ cases of H5N1 infection is largely unanswered. To date, there have been no seroprevalence studies (blood antibody) to support this notion. The only study that has been released was done in a Cambodian village, and it found no evidence of `silent’ infections.
Hopefully, someone somewhere is actually doing this research and we will get answers soon. For now, all we truly know is that among reported cases, confirmed by laboratory testing, more than 60% of infected patients have died.
The last assumption, that the next pandemic will be caused by the H5N1 virus, is once again, speculative.
This virus is certainly well positioned to be the next pandemic. It is highly pathogenic, it has a large geographic spread, and it has now been proven to infect a wide variety of hosts, including cats, dogs, pigs, and humans. It is lacking only one thing; the ability to be easily transmitted from human to human.
But there are other pathogens out there, and while we are focused on the H5N1 Bird Flu, it isn’t the only pandemic threat. There are several other influenza strains, other than H5N1, that could make the jump to humans at any time. XDR TB (Extreme Drug Resistant Tuberculosis) is of growing concern around the world, and it too has the potential to cause a world health crisis. While not as infectious as influenza, it could be the next scourge to sweep the globe.
As you can see, there is much uncertainty in all of this. Much we don’t know. In the face of the unknown, our best defense is to prepare to fend off all threats. We can best do that by funding research, building a solid public health infrastructure, and preparing on a personal, state, and national level to weather a pandemic crisis.
For you see, ignorance isn’t bliss.
And what you don’t know can hurt you.
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