Perhaps if we were not stuck with textbooks that taught genetics in Mendel's words, or evolution in Darwin's, it wouldn't be so hard to understand the emergency, virulence, and eventual resolution of a pandemic virus like the new swine flu. And perhaps if we had far better public science education, there wouldn't be so many diaries suggesting that the potential pandemic is an insidious terrorist or government plot. As it is, CDC and WHO have major jobs in public education as well as in public health this week.
Let's start here. Viruses aren't add ons to our genomes; in fact, they may be the origin of most of the metabolic functions in modern cells. Evolution doesn't always occur by mutations (copy/paste accidents) but at least as often by "deliberate" viral transposition (if you can anthropomorphize anything a virus does as deliberate.)
And pandemic viral infections have relatively predictable origins, courses, and eventual resolutions. It's all evolutionary biology (despite what Fundamentalists would have us believe.) Jump for easy review.
A virus is basically a small segment of genetic material (DNA or RNA) wrapped in a protein coat. The protein coat is what a cell recognizes and potentially fights off; if not, the genetic material can enter the cell and have its way. Eventually the cell explodes with new viruses it has made--some of which may contain not only the genetic material it came with, but fragments of more. Viruses are constantly hybridizing; two or more viruses in the same host might combine, while bits of the DNA they brought in can become a permanent part of the host organism.
The new virus is identified as H1N1--
A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 1 and neuraminidase 1. The H1N1 subtype was responsible for the Spanish flu pandemic of 1918 and for swine flu.
It wasn't created from some "animal human hybrid experiment" (as certain GOP congresspersons might suggest) or deliberate bioterrorism, but by a process that viruses have conducted for billions of years. Viruses were probably the primary engine in evolution.
...viruses, as an evolutionary lineage, predate both the formation of modern cellular life and use of DNA, but that they developed after the three main branches had already split. Forterre argues that DNA was a viral innovation, developed after the hosts had evolved defenses that targeted viral RNA. The initial DNA viruses would have been generalists, and could have freely exchanged their DNA metabolism genes, or adopted RNA metabolism enzymes from hosts in any of the three branches. As they specialized to infect a specific branch, they locked an idiosyncratic combination of DNA enzymes in place. Eventually, in each of the three branches, an infection would fail due to a defective virus, and the resulting DNA genome would be trapped in a proto-cell. Due to its chemical stability, selective pressure would favor moving host genes to the DNA genome, eventually resulting in a complete, DNA-based cell. Life would be off and running.
The process of gene translocation has many (almost always negative) effects on today's human genes besides infection. Moving a specific gene from a chromosome to another where there is not an adjacent "control segment" can mean that it has unpredictable functions in the cell, such as turning an otherwise healthy cell into a malignancy. That's why viruses are suspected as the cause or one of several causes of diseases like cervical and head/neck cancers and lymphoma.
It's clear that pandemic viral infections aren't new. Now that researchers are looking for them, evidence of past infections that have run rampant and then lost their virulence seem to be everywhere. Here's one report:
French researchers have resurrected the "Phoenix virus," a "fossil virus" that lay dormant in the human genome. The retrovirus infected our ancestors millions of years ago, and is apparently still infectious in its new revivified form...The researchers showed that the newly crated virus could infect a variety of human cell lines and replicate. But its infectivity was extremely low, perhaps because human cells have evolved resistance against such viral invaders.
AP reports on 3 recent pandemics:
A glance at the last three pandemics:
_ 1918. The Spanish flu pandemic that started in 1918 was possibly the deadliest outbreak of all time...it killed about 40 to 50 million people worldwide...
_ 1957. The 1957 pandemic was known as the Asian flu...caused about 2 million deaths globally...
_ 1968. The most recent pandemic, known as the Hong Kong flu, was the mildest of the three pandemics this century... About 1 million people are estimated to have been killed by this pandemic, an H3N2 flu strain.
The explanation for each of these outbreaks is similar; the virus changed its coat:
Major changes in the surface glycoproteins of influenza virus - called antigenic shift - lead to worldwide epidemics of influenza known as pandemics. There have been six instances of antigenic shift since 1889. In that year, H2N2 viruses circulated, followed by H3N8 in 1900, H1N1 in 1918, H2N2 in 1957, H3N2 in 1968, and H1N1 in 1977. Each pandemic strain carries HA and NA proteins that have been absent in humans for many years, and therefore immunity is either very low or nonexistent.
In each case, as in the recent outbreak of West Nile virus, the pathogen didn't go away. As the pool of non-resistant hosts diminished, the virus itself lost virulence through a process that's not clearly understood. (After dramatic predictions on West Nile virus, immunologists found that it seemed to diminish on its own and a majority of well subjects tested eventually showed some evidence they had been exposed and developed resistance on their own. But in a strange contradiction, the less virulent the virus, the more likely it will become pandemic (because really sick people stay home or get treatment, while moderately sick people may try to go to work, ride mass transit, or go shopping.)
Spanish Flu is now extinct in humans (or buried harmlessly in our genomes.) The "Swine Flu" is a close relative. One eerie echo of that time though is being heard today: In the Spanish Flu, young people were more susceptible to the disease and that's recurring now. Young, healthy people are getting it more often than seniors.
So what does all this evolutionary evidence tell us about today? First, that paranoid blogs about deliberate creation of the virus like this have no basis in science.
The suggestion is clear: the virus was frozen in a laboratory freezer since 1950, and was released, either by intent or accident, in 1977. This possibility has been denied by Chinese and Russian scientists, but remains to this day the only scientifically plausible explanation.
There are ample natural mechanisms for viral recombination without seeing terrorists behind every flask.
Second, that the virus must be slowed. The only proven remedy for pandemic infection over the millenia is time. Mexico's actions this week to separate people are important, but far more might be needed. The sorts of "martial law" actions (like closing schools, limiting meetings, and rationing antivirals) represent political pitfalls for leaders but are absolutely necessary to limit spread. In today's global society, its inevitable that some nations will be more aggressive in these actions than others and therefore some limitations on travel will be needed.
That's why it's so important to avoid ignorant tinfoil theories; our leaders will get a lot of resistance from the uneducated and deliberately ignorant. We need to muster all the support we can at this point for tough actions.
Official CDC site