Irradiated by LabRat
So, mere years after the bird flu that cut a swath of destruction inches wide across North America, the new flu concern is swine flu part two, Mexican boogaloo. Scientists are warning of a pandemic, and an awful lot of folks I know are stocking up on their Purell wipes.
Me, I’m not particularly sweating it right now. I’ll probably get a flu shot when they get the strain sorted out, but then I think flu shots are a good idea anyway. Do I think we’re looking at the potential for an apocalyptic attack on civilization, Spanish Flu the Sequel? Too soon to tell.
First, a little background on influenza, our starring virus. Influenza has the relatively uncommon viral ability to infect several different unrelated species; while influenza is actually quite the slut of an upper respiratory virus and can get at a very wide range of host species with various levels of consequence for the host, the ones we hear the most about are birds and pigs, partly because of the bird’s mobility and partly because both come in domestic forms that have a great deal of interaction with humans. This versatility gives influenza one extra leg up in the evolutionary arms race that is being a pathogen- it mutates with tremendous speed as it picks up new genes and adapts across species. This is why you need a new flu shot every year instead of being good to go with a handful in a lifetime as you are with a human-only species like smallpox. Influenza strains are like popular dance tracks- each new host and generation of host provides its own remix.
This is why influenza is so popular in apocalyptic scenarios; their evolutionary chops make it virtually impossible to produce targeted vaccines and drugs against it, and its versatility in choice of host and method of transmission makes containing it equally impossible once a successful strain gets legs. The way that influenza jumps across multiple species also makes it scarier in one other respect- the normal evolutionary pressures on pathogens are blunted by the way a strain “grown” in one species may do something drastically different in a new one. Normally, an upper-respiratory virus is under pressure to be very successful at infecting, but not to be particularly virulent*; a host that feels well enough to be up and walking around and coming into the office saying “itds justg a liddle code” is a host that’s spreading the virus further and making it more successful. Diseases that depend on on a method of transmission independent of the host’s mobility- like insect-borne diseases and water-borne diseases in regions with poor sanitation- can afford to be more virulent than respiratory viruses. Influenza’s rapid mutation rate and multiple hosts make it a bit of an exception**.
The other reason influenza is so popular as a terrifying pandemic is that we’ve already HAD a terrifying pandemic from one particularly awful strain, the Spanish flu. World War I claimed its bodies, but the flu was responsible for far more of the generational gutting of the period- its death toll was double that of the war. One of the things about the Spanish flu that’s gravely cited in discussions of the epidemic is its odd pattern of fatality- it included a disproportionate number of the young and perfectly healthy. The morbidity and mortality graphs for “normal” flu look like U’s; the very young and the very old, those with undeveloped or compromised immune systems, get sick and die far more often. The 1918 pandemic’s morbidity and mortality graph looked more like a W- there was another big spike in the middle, healthy adults. Right now the hot theory for how this could have happened is the cytokine storm, which boils down to an overreaction by a robust immune system causing more damage than the virus on its own could have. It’s been observed in mouse models infected with the 1918 strain, but is overall not very well understood at all. Aside from the general lack of clarity into what exactly is involved in a “cytokine storm”, there’s plenty of obfuscating factors- the data isn’t great, and there’s also the role that the war itself played in creating massive congregations of young men in poor (immuno-suppressing) conditions and then letting them cough on each other for indefinite periods.
The major problem with projecting a 1918 style pandemic from a modern flu strain is that, in developed countries especially, a number of things have changed since then. In both normal flus and the Spanish flu, the number one killer isn’t/wasn’t influenza itself so much as it was bacterial pneumonias and other opportunists- once the flu set in and started knocking down the immune system and tearing up tissues, secondary infections would set in and finish off the weakened patient. The super-virulent flu of 1918 had its share of acute cases in which (apparently) severe damage to the lungs and intestines rapidly followed infection and death occurred soon after- but these cases were far from the majority. One of the reasons this new “swine flu” is gathering such attention is that this may have happened to some of the Mexico City fatalities- but one of the things missing from the media reports is how very few of the fatalities have been confirmed by culture to BE swine flu, just as the cases in the US have a big question mark attached to them. Unfortunately, our news cycle is a lot faster than our laboratories are. Either way, even if the new flu is every bit as virulent, the developed world isn’t likely to see anything like 1918′s fatality rate- simply because we have medical technologies hospitals of the time lacked, like antibiotics and antiviral agents for more acute cases.
The thing about the word “pandemic” is that while it technically means just the same thing it always did- a global epidemic- the differences in fatality rate are now tremendously more local than they were even as late as the beginning of the twentieth century. This is why, when we hear about some scary new flu, SARS, or other virus du jour, the fatalities seem to kick hell out of the less developed world and then virtually halt by the time they hit first-world nations; not only is the medical treatment available of a much higher quality for victims, but the level of sanitation and rapid identification of victims tends to put a huge damper on the spread of infection. This is why ordinary flu is regarded in the US as interchangeable with “a sucky week off from work”, whereas if you live in rural Madagascar it’s a serious risk of death. To put it in some perspective, bear in mind that right now the worldwide death toll for all influenzas hovers around the hundreds of thousands… whereas deaths from simple diarrheal diseases, particularly for children, are in the millions.
So, could the swine flu be as virulent as the 1918 flu? It’s a possibility. There’s not near enough known about it yet to tell, though it’s good that people are getting serious early about trying to contain it. Should you listen to the media? Take with several large grains of salt- reporters tend to be no better educated on the subject than “the flu was a horrible pandemic once!”. Should you worry about the flu-caused collapse of civilization? Really, I wouldn’t.
*Virulence: the technical term for just how severely a disease kicks the shit out of its host. A disease like herpes has very low virulence, whereas one like ebola has extremely high virulence. Infectivity- how good it is at breaching immune defenses and setting up shop- is an independent trait.
**This may well be one reason the 1918 pandemic lasted less than a year- terrifying as it was, it was also not very fit by virus standards.