Swine Flu Will Likely Sicken Billions But Kill at a Low Rate

By Eliza Strickland | May 12, 2009 1:55 pm

pandemicA “fast and dirty” analysis of the spread of swine flu thus far has led researchers to believe that the virus will eventually turn into a true pandemic infecting about a third of the world’s population–but they hasten to add that the analysis also suggests that the flu doesn’t have a devastating death rate.

Lead researcher Neil Ferguson, a member of the World Health Organization’s emergency committee for the outbreak, says: “This virus really does have full pandemic potential. It is likely to spread around the world in the next six to nine months and when it does so it will affect about one-third of the world’s population. To put that into context, normal seasonal flu every year probably affects around 10% of the world’s population every year, so we are heading for a flu season which is perhaps three times worse than usual” [BBC News].

The analysis, published in Science, also roughly estimates that the flu has a fatality rate of .4 percent, meaning that it kills 4 people out of every 1,000 infected. That makes the swine flu virus about as dangerous as the virus behind a 1957 pandemic that killed 2 million people worldwide. But it’s not nearly as lethal as the bug that caused the 1918 Spanish flu pandemic [ScienceNOW Daily News]. Seasonal flu has a fatality rate of less than .1 percent, and kills more than 250,000 people each year.

While global hysteria regarding swine flu has subsided somewhat, confirmed cases continue to mount. Yesterday, the World Health Organization said that swine flu has been confirmed in 4,694 people around the world, with the bulk of the cases in North America. Sixty-one people have died, including 56 in Mexico, three in the U.S., and one each in Canada and Costa Rica, health officials said. The U.S. confirmed 2,618 cases in 44 states, according to the Centers for Disease Control and Prevention [Bloomberg].

One mystery is why the virus seems to cause more severe symptoms in young people: U.S. health officials say the median age of people hospitalized with swine flu is 15 years old. Researchers say that could be a troubling sign that young and healthy people are more vulnerable to the virus–but in a contradictory finding, researchers have also found that many of the people who have died from swine flu had preexisting health problems. One possible explanation, says Ferguson, is that flu viruses that resemble the current swine flu virus may be commonly seen in normal seasonal flu epidemics. Adults are more likely to have encountered those viruses and developed immunity to them, and it may be that in some cases this immunity is enough to provide protection against swine flu [Nature News].

While the findings of this first analysis are far from definitive, they do suggest that world health officials should quickly decide whether to start production of a swine flu vaccine, which could be ready before autumn comes to the northern hemisphere, possibly sparking a new outbreak. “One of the key decisions which has to be made this week by the world community is how much do we switch over current vaccine production for seasonal flu to make a vaccine against this particular virus?” [BBC News], says Ferguson.

Related Content:
80beats: Swine Flu Outbreak May Subside, but Officials Are Wary of a Second Wave
80beats: Genetic Analysis of the Swine Flu Virus May Indicate a Less Lethal Threat
80beats: World Health Organization Ups Pandemic Alert Level for Swine Flu
80beats:  As Swine Flu Spreads, Focus Shifts to a Potential Vaccine
80beats: Fears of a Swine Flu Pandemic Increase as the Virus Goes Global
80beats: Deadly Swine Flu Outbreak in Mexico City Prompts Fears of a Pandemic 

Image:iStockphoto

CATEGORIZED UNDER: Health & Medicine
  • FactChecker2

    Okay: so more than three times as many people (compared with the seasonal numbers) may get this novel pandemic strain of flu. (33% attack rate vs. 10% attack rate)

    And four times as many of the sick will die than in the normal flu season (0.4% Case Fatality Rate compared with less than 0.1% during an average flu season.

    So if there are an average of 36,000 flu deaths in the U.S. per year, this swine-origin flu virus could produce more than 432,000 deaths in the U.S., if the estimates in the article come to pass.

    And also, in the average flu season, most of the 36,000 deaths are in the elderly or the very young. But this new swine-origin flu virus seems to be attacking mostly young adults and teens, and barely touching the over-50 crowd.

    So we may be talking about more than 432,000 deaths of otherwise healthy teenagers and young adults.

    Glad you see this as killing “at a low rate.” There’s always a worser case out there somewhere, isn’t there?

  • Rocket

    It appears to me that the US death rate is vastly different than the global rate at approximately .12%. That is not materially different than the seasonal flu. If that holds, then the number of deaths will be determined by whether the prediction of a 300% increase in infections materializes. A responsive immunization program in the US seems to be a no brainer.

  • Don

    Well, low compared to the Spanish Flu. And minuscule compared to H5N1 (heaven forbid it should become as contagious like swine flu without losing its virulence).

  • Scott

    That still comes to 8-9 million deaths worldwide. I’d say that qualifies as pretty severe.

  • FILTHpig

    Really FactChecker2? Worser? Maybe you should say “more worse” or “a lot more worser”, sorry, I had to say it…

  • Gwenny

    Evolution at work, folks. We are stressing the environment and the environment is stressing back.

  • jon

    gwenny, this has absolutely nothing to do with evolution. It has everything to do with peoples’ immune systems.

  • szai

    Everything living has everything to do with evolution. This virus has evolved to affect mainly young adults and teens. Whenever a certain portion of a population is killed off, and the survivors are left to carry on, well, simply put, that’s natural selection at work. You could argue that the virus could be at least partially man-made, and thus not “natural”, but how is a human using a micropipette any less natural than a chimp using a stick to catch ants?

  • Madeleine

    New viral strains don’t arise because of general stress to ‘the environment’. It’s not like some kind of karmic payback. It’s more of a “given enough time, something like this is bound to occur” situation.

  • cr

    That .4 % CFR is, “best case”- which will not be available come surge.

    Toss-up which happens first;
    “JIT” PPE delivery-and the other 80% of our imported medical drugs/supplies stop,
    or too many HCW are sick/dead, or,
    “planned for years to be ‘scarce’” Tamiflu runs out-(already people in the US and elsewhere are being denied it, who should have been on it within 48 hours of symptoms) or
    the beds/ICU units/vent fill up.

    [And the 'collateral deaths start; deaths caused by pandemic disruptions were not taken into account in 'planning'- indeed hardly anything useful was done anywhere;
    local officials have gone from 4 years of, 'hope pandemic doesn't happen' to,
    'hope there's an effective vaccine in quantity in time' - Too late!]

    Already hospitals in the N.hemisphere have cancelled non-emergency surgery because panflu cases are taking up all available resources.

    -As we get into, “altered standards of care”; no antivirals and no hospital available,
    then the CFR will rise to its, “untreated” CFR, as was seen in Mexico at the start,
    which the WHO put at 2% average CFR
    - some age groups had much higher; up to 5+% CFR-
    see the WHO weekly report for May 22, 2nd page in for CFR by age decade:
    http://www.who.int/wer/2009/wer8421.pdf
    or, see how Argetina and Guatemala are doing now;
    try the, “PFI Pandemic Flu Information Forum” for news.)

    Since the ‘planned’ NPIs were abandoned for some last-minute ‘status quo’ commerce and profit (just as authorities did in 1918, with few exceptions- but, the cities that proactively did the most to reduce transmissions lost the fewest people)
    we are in for, “tragic” Consequences.

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