The 2009 Pandemic Flu: A Premature Retrospective

We may have been lucky once again. The H1N1 / Swine flu epidemic which was first reported in Mexico in 2009 hasn't proved as deadly as early reports suggested it might be. It's influenza. It's a pandemic. It will kill a lot of people over the next three years. But it doesn't look like it will be anywhere near as deadly as the flu pandemic of 1918. It looks like it is another near miss, which means that we may have the chance to learn some lessons from the current outbreak...

The outbreak of H1N1 in Mexico City in March 2009 looked deadly. By April 30th 2600 suspected cases had been reported and over 100 were reported to have died. On April 29th the World Healthy Organization had raised its pandemic alert level to phase 5 – indicating that we should prepare for a worldwide pandemic. Things looked grim.

But they weren't. The strain of flu turned out to be much less lethal than first thought – about the same or less than normal seasonal flu. When the WHO declared that the outbreak had reached pandemic status on June 6, it was almost a non-event.

It's worth spending some time on just why this happened, because it is very likely that this delay in determining the clinical attack rate (percentage of people exposed to the disease who develop symptoms) and mortality (percentage of people who die after catching the disease) and thus uncertainty about the danger posed by a disease will be repeated in future. Next time the authorities may err on the side of delaying or downplaying a pandemic: they may or may not be right when they do.

One of my wife's friends is a nurse is in the emergency department of a hospital. When we discuss childhood activities with her she has (to our minds) a very distorted view of their dangers. She sees a large number of children who have injured themselves while doing martial arts, tobogganing, or skiing so she sees these activities as excessively dangerous. She doesn't see the children who successfully climb a tree: only those who fall.

With pandemic flu there is the same problem. A hospital sees only severe cases. The tests required to determine the actual attack rate and mortality of a flu virus need to know how many people were exposed to the virus even though they did not develop severe symptoms. This is normally determined (in retrospect) by examining a sample of the population to determine how many have antibodies to the virus and have therefore been exposed to the disease. It takes time to do this. In the meantime, the only statistics available are the number of people with the virus arriving at the hospital and the number of people dying of the disease.

There's also a problem with testing. Suppose someone dies at the hospital of pneumonia. We do some tests to see if they had H1N1 flu when they developed pneumonia. They did. What was the cause of death? H1N1 flu. But if we hadn't been specifically looking for H1N1 flu, the death would have been ascribed to pneumonia. By testing, we start moving deaths and illnesses into the H1N1 column.

So our luck has held so far. The flu is spreading. It is a pandemic. It will kill people. If history is any guide, it will spread and kill a lot of people over the next three years. But it does not appear to be a deadly pandemic like that of 1918.

I classify this as a near miss. The good side of near misses is that we get to learn from them for the future. What can we learn so far?

What we can learn about pandemics and the world?

Let's take a look at some of the aspects of the 2009 H1N1 (Swine) Flu outbreak which may not have been obvious beforehand:

  • Flu spreads quickly. Between the first media reports outside Mexico and a WHO Phase 5 pandemic warning took about a month. The virus was reported in over 40 countries in a matter of weeks, and most attempts to stop the international spread of the virus were abandoned. Influenza is infectious before symptoms are visible, and, if it is capable of human-to-human transmission, its spread is only really limited by the availability of new people to infect.
  • Widespread economic effects. Places where people might gather were shutdown in Mexico City (from churches to restaurants) and all non-essential businesses closed for a period of time. Schools closed in other countries where a single student might have been exposed to the flu. In Hong Kong a hotel with 300 guests was quarantined for a week because a guest had the flu. The Mexican tourist industry shut down, with flights being cancelled and cruise ships being diverted.
  •  International trade and travel affected. Contrary to WHO recommendations, pigs and pig products that originated in countries where the swine flu was detected were banned. Students from Canada visiting a province in China were (ineffectively) put into involuntary quarantine. Flights to some destinations are being checked for sick passengers, and passengers are being temporarily detained if it is believed that a passenger might have influenza.
  •  Antivirals such as Oseltamivir (Tamiflu) worked on this strain but did not work on last year's seasonal flu. We can't rely on such drugs to be effective in a future flu epidemic.
  •  The WHO Pandemic Phases don't take account of mortality. Seasonal flu is in Pandemic Phase 6, kills a few hundred thousand people each year, (mostly those with compromised immune systems), but is not something we worry about. Concentrating too much on the pandemic alert phase may give us a distorted picture.
  •  Contractors with flu can't afford to stay home. It has been reported that the herd of pigs in Canada that caught Swine Flu may have done so from a contract carpenter who did his job even though he had some flu symptoms. If you don't turn up, you don't get paid. Welcome to one of the side-effects of the new economy.
  • People panic. Did you notice the underlying atmosphere of panic among the less informed? While models may predict the number of staff who will be killed, get sick, or take time off to look after a sick family member, it's unlikely that models will accurately predict the number who are absent due to fear of infection. You can get a good idea of the misinformation being propagated and some highly dubious products being promoted to panicked individuals by doing a search on Twitter ( ).

What we can learn about our own readiness?

Now is the time to start reviewing what happened with our own pandemic preparedness while memories are fresh:

  • Did you activate you pandemic contingency plan? When did you activate it? Did you know how to activate it? Were you reviewing the possibility of a pandemic frequently enough to react before the first news reports started appearing?
  • Did you remind staff of the importance of basic hygiene? That the best ways to avoid getting and transmitting the flu virus are frequent hand-washing, coughing into a sleeve rather than a hand, and staying at home if you feel sick?
  • Did you increase the disinfection of common work areas?
  •  Did you make sterilizing hand-cleaner available?
  • Did you make sure your staff had a reliable source of information, rather than relying on rumor and gossip?
  • Did you have a method of increasing social distancing? Were you ready (or did you) to switch to telecommuting? Did you start using teleconferencing? Or were you assuming that you had more time to buy equipment, train staff, etc.
  •  Did you limit staff travel to / from affected areas? Did you restrict visitors?
  •  Were you ready to institute split-shifting or other techniques to increase social distancing between groups of staff?
  •  Did you have enough stocks on hand to cope with possible disruptions to supply?
  •  Were you prepared for any possible restrictions on international trade or travel?

And finally…

Have you seen the complacent "it didn't kill us so everybody is making a fuss over flu pandemics for nothing" attitude yet? You will.

7 July 2009

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