April 06, 2013
H7N9 Virus In China A Pandemic Threat?
Laurie Garrett, she the author of The Coming Plague: Newly Emerging Diseases in a World Out of Balance, has a piece in Foreign Policy about worries that the H7N9 influenza virus in China could break out into a major pandemic.
Here's how it would happen. Children playing along an urban river bank would spot hundreds of grotesque, bloated pig carcasses bobbing downstream. Hundreds of miles away, angry citizens would protest the rising stench from piles of dead ducks and swans, their rotting bodies collecting by the thousands along river banks. And three unrelated individuals would stagger into three different hospitals, gasping for air. Two would quickly die of severe pneumonia and the third would lay in critical condition in an intensive care unit for many days. Government officials would announce that a previously unknown virus had sickened three people, at least, and killed two of them. And while the world was left to wonder how the pigs, ducks, swans, and people might be connected, the World Health Organization would release deliberately terse statements, offering little insight.
Click thru and read the whole thing. 9 dead in China so far. But no reported case of human-to-human transmission. One worry: H7N9 spreads in poultry without killing.
So are we about to have a massive global killer pandemic from H7N9? The odds are against it. We've witnessed several viruses (e.g. SARS) jump from animals to a handful of humans, kill a large fraction of the infected, and not go on to cause a global pandemic. However, it is well within the realm of possibility that we will some day get hit by a global pandemic on par with the 1918 flue which killed tens of millions globally.
My take on killer pandemics: As compared to other natural threats an especially lethal influenza virus seems like small potatoes. If you have the cash, self discipline, and sufficient smarts you can greatly reduce your risks of dying from such a virus by taking steps to isolate yourself (preferably in a small work group) while a vaccine gets developed and manufactured. Though note that old people have immune systems which do not respond well to influenza vaccines.
Randall Parker, 2013 April 06 12:06 AM
Read "Plague Time" by Paul Ewald for an evolutionary medicine approach to pandemic prediction. The pre-conditions for something like the Spanish Flu appear to be a large non-ambulatory population of victims in close proximity, which allows enhanced horizontal transmission with corresponding evolution of virulence. Of more concern than something like the Spanish Flu, are stealth viruses like AIDS -- where the victim's asymptomatic period as a vector is long -- and bacteria that have evolved antibiotic resistance. Of secondary concern are diseases like malaria where close proximity of the non-ambulatory victims is made unnecessary by highly mobile vectors, such as mosquitoes.
Anything we could say about potential plagues is speculation. Plagues occurred in the past so it's likely we'll see one in the future. The populations are larger so there is more chance of one developing. OTOH, we have better medical technology so we're much better able to nip it in the bud. Plagues don't happen every day. But we haven't seen anything significant in almost a hundred. With the obvious exception of AIDS. But that's not particularly contagious as long as one avoids high risk behaviors. It seems more likely that we'll see a return of the old infectious diseases that were all but wiped out a few years ago. I'm thinking along the lines of drug resistant TB. If one of them mutated to be drug resistant and then mutated to become highly infectious it could be real problem.
Thanks for the book reference. I just ordered it.
I've read claims that the trenches in WWI and military hospitals in close proximity to farm animals helped the Spanish Flu develop. I've wondered whether current conditions are less favorable toward development of a new very virulent strain. But the total human population is much higher and Africa, for example, has some dense and poor cities. India has high population density too.
From what I read regarding the "Spanish Flu", it actually originated on a Nebraska farm, and was taken to the local recruitment center where it spread.
Don't get too focused on China.
There is a lot of speculation on the origin of the Spanish Flu but its true origin has never been confirmed. It's speculated it mutated from another strain in either the US or France. Most flu strains originate in east or southeast Asia during the rainy season. Over the next few months they spread to other continents before dying out. They never go the other way because, by the time someone from the west brings it back, Asians have already been exposed and are immune.
That's why the death tolls from around the world are so interesting. Estimates put fatalities at 50-100 million. Large numbers of Americans, British, French, West Africans, Indians, Indonesians, Japanese and Samoans died. Did you notice anyone missing from the list? Chinese. I suspect Chinese were already immune because the strain originated there in a less lethal form. After spreading overseas, it mutated into its more lethal form. But when it returned, Chinese were already immune because the population had already been exposed to the less lethal form.
H7N9 is worse from an immunity perspective because it does not normally infect humans. Could be that few will have any existing immunity to it.
Unlike many, this particular flu does not infect pigs. However, it has characteristics that are potentially dangerous:
(1) It appears to evoke a weak immune response in humans. This makes it less susceptible to vaccination.
(2) It requires little genetic drift before it would spread between humans, according to genetic analysis.
Many virus strains immune to antibiotics are not immune to micronized silver. See here a 100% die-off of the HIV strain.