Influenza A(H1N1) cases: graph of WHO data, discussion of media coverage

In the next 30 years, seismologists have determined that the chance for a magnitude 6.7 or later earthquake in California is over 99%. One can easily see based on the historical record that this is a safe prediction. In the last several hundred years, Californians have not had a period of 30 years go by without such an earthquake.

Similarly, influenza outbreaks follow a regular pattern. Roughly every 50 years one can expect a influenza pandemic that kills a million or more people worldwide. (What’s less frequently cited is that every year, the regular flu kills up to 350,000 people worldwide, mostly the elderly.) In recent history, the Hong Kong flu of 1968 killed up to 1 million people. The Asian flu of 1957 killed up to 1.5 million people. And the 1918 Spanish flu outbreak killed up to 40 million people worldwide.

It’s understandable, then, why people were concerned with swine flu and why there was so much media coverage. What if it turned out to be one of those catastrophic pandemics that kills millions of people? What if we couldn’t (or can’t) create an effective inoculation? It’s rational to be cautious, and to pay attention to the news.

On the other hand, in recent years we’ve seen coverage of previous threats from SARS, avian flu, and others, and they turned out to be relatively minor events. In some cases we overreact. It certainly seems to me that mainstream media overhyped the threat from swine flu and created a sense of panic that was unwarranted from the facts. Now that coverage has faded, I’m sure most people aren’t really thinking about swine flu any further.

The thing is, it’s not really over. Worldwide cases have climbed to nearly 20,000, and the number of deaths is over 100. In the U.S., there are currently 17 fatalities. (The media really only covered the first two victims.)

From here, swine flu could fade away into nothing, or it could suddenly explode. The latter outcome seems increasingly outcome, however. And here’s some data to support why I believe that.

The World Health Organization (WHO) has been releasing data for 41 days; over that time, they’ve provided 43 updates as I write this. Earlier they released two updates a day. Currently the updates come every few days.

WHO update swine flu case data, including number of cases, deaths, and cases per day

WHO swine flu case data, including number of cases, deaths, and cases per day (click to enlarge)

The graph above shows the number of new cases reported per day, as a line. In addition, as an area, the number of confirmed cases (yellow) and confirmed deaths (red) are also included.

By profession, I’m a numbers guy. Quantifiable analysis is my preferred approach for investigation. So starting from the beginning, I monitored the numbers of confirmed cases, countries, and deaths from the WHO updates and analyzed how many cases per hour, day and week.

With a pandemic, what we worry about is exponential growth (100 cases becoming 200 cases becoming 400 cases becoming 800 cases). Even linear growth can be scary for a pandemic if the numbers are large enough (50,000 cases becoming 100,000 cases becoming 150,000 cases). But that’s not what we have here, judging by the WHO’s numbers.

In fact, the number of new cases per week has been steady for the last three weeks at about 4,400 new cases a week.

There are many disclaimers that should be associated with the WHO’s numbers. Who knows what politics play into the process, and who knows if the count of confirmed cases is constrained by laboratories crushed with tons of undiagnosed cases that are even now uncounted. And the number of as-of-yet unreported cases (especially from third world countries) is a total unknown. You can tell from the extreme variability in the number of cases per day that human factors influence the reports.

However, after looking at nearly five weeks of data, it’s easy to assert what the media has already decided — there’s no exponential growth, and not even significantly increasing linear growth. Note instead how the cumulative number of cases appears to be very smoothly linear.

Given the relatively small number of cases compared to other threats, it’s clear the news cycle for swine flu is dead and not returning unless something completely unexpected happens, despite scattered reports of ongoing school and business closings.

So before this story fades into the sunset, the question to ask is if the media and health workers reacted appropriately. Was the coverage sufficient or insufficient, was it overblown or underblown or exactly right?

The June issue of Lancet contains a story (reprinted here) arguing that the amount of coverage was proper, and that due to quick action from health workers and cooperation from a fearful public, a crisis was averted.

I’m not qualified enough to disagree, but it seems to me the most important factor was the nature of the swine flu itself, and just how contagious it was. The evidence shows that it just didn’t spread that quickly — it wasn’t that virulent.

But it’s quite possible that because of the coverage, we put in place behaviors that saved ourselves. By analogy, consider Y2K (where we worried that computer code that used 2-digit years instead of 4-digit years would lead to buggy behavior when the software assumed the year 1900 instead of 2000, and that these issues would affect critical facilities and cause widespread technological disasters). There was enormous media coverage. Speculation was rampant, including fears of widespread power failures and nuclear facility mishaps, and some predicted wholesale societal breakdown. Yet of course when January 1, 2000, rolled around, very little happened (other than some big hangovers). So, overblown, right? Maybe not. I know first-hand how much effort engineers and developers put in ahead of time to certify certain systems, reprogram others, and generally make sure that everything would continue to work. To an outsider, Y2K certainly seemed overhyped. And much of the speculation (including the concept that embedded chips in cars and toasters would malfunction and shut down) was in fact ridiculous. But most computer professionals know that, while the coverage was certainly hysterical at times, there were instances of genuine bugs (that could have affected paychecks and so on), and that most of these genuine issues were averted due to foresight, prudence, and hard work.

I’m no medical professional. While I immediately dismissed swine flu fears and coverage as overblown, maybe that’s because I’m an outsider, not seeing all the hard work that took place to make sure the disaster was averted before it became a deadly pandemic.

Aside from those very unfortunate people who died due to swine flu, in the end, the economic impact may be swine flu’s longest-lasting legacy. Several reports show that Mexico tourism dropped by huge percentages, even in regions where there were zero swine flu cases. Recovery to previous levels will take time. (I’m told there are some amazing travel bargains to Mexico now.)

EDIT: Based on feedback from Kevin Fox, I updated the graph to simplify it a bit, and to use just regular calendar dates instead of dates and WHO update number. That corrected the problem whereby the variable number of days between updates made the cumulative number of cases look to be accelerating.

5 Responses to “Influenza A(H1N1) cases: graph of WHO data, discussion of media coverage”

  1. Paul Reed-Peck Says:

    Hi Stephen,
    Would you be able to provide an update on the number of cases per day graph with the information received from the WHO this week?
    I have a near-hysterical girlfriend who I’m trying to reassure regarding the impact of swine flu, so this would come in very handy!

  2. Stephen Says:

    Paul, it’s updated! Even the WHO (who must protect their budgets and be cautious) assesses it as “moderate” at this point. So she can definitely back down from “near-hysterical” and be merely “moderately” concerned. 🙂

  3. ArnoL Says:

    You should update your graph (btw, it’s very surprising that you’re neraly the only one to publish it on the web !), the last figures show 2k to 3k new cases by fay, and , if it not change all your conclusion, it moderates it a little bit ..
    source :,confirmed

  4. Jasper Says:

    Hi, interesting analysis. Was doing similar analysis based on WHO data just to see if spreading is growing linearly or exponentially. Could not find a database of the data though, which means copying pasting the WHO data. So only took number of datapoints, until I found above analysis. Added this to my graph, and see that since June speed of spread has gone up (steeper slop), though I do agree to overall conclusions above.
    Need to take into account though summer season (virus less active), so would be interesting to see a separation for northern vs southern hemisphere.
    Here in Netherlands expectations are still that we will see a real epidemic after summer (Septermber onwards).

    Do you if the WHO data is accesibale in a database format anywhere, so that I can easily keep track? Thanks for interesting analysis.

  5. Stephen Says:

    Thanks Jasper. I scoured the WHO site and couldn’t find any useful data format, so I’ve been entering some of the data from their daily updates manually. I’d be happy to e-mail you my Excel file — just send a request to estephen here at

    I’m about to write another update.

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