Investigating the epidemiology of flu, Big Brother style

In these LabLogs I’ve talked endlessly about how we can’t predict the start of an influenza outbreak. Despite this, you might be surprised to learn that there are many things still to learn about how influenza is transmitted from one person to another.

When someone with influenza sneezes they produce big bits of snot that tend to settle on surfaces that get touched by other people. Smaller particles are also produced by the sneeze and can hang around in the air as what we call aerosols. Importantly, we don’t really know the relative amount of how much influenza is spread by these two different processes. The reason this is important is that it could help us understand the best ways to block the spread of flu.

Surprisingly, to understand this, Professor Van-Tam and his team have been deliberately infecting a group of volunteers with flu and then putting them in a Big Brother type environment with other non-infected volunteers and measuring how the virus spreads.

All volunteers were asked to regularly wash their hands in order to make sure they didn’t get infected by touching contaminated surfaces. Importantly, the non-infected volunteers were split into two smaller groups: one was given a protective visor to cover their whole face and the other wasn’t.

We know there are three possible ways that flu can spread from person to person:

  • Aerosol – these are the small particles containing the virus, which in this experiment can easily be drawn around a protective visor. All volunteers in the experiment could get infected in this way.
  • Droplets – large particles of snot that hit the protective visor but won’t be drawn around it. Only the volunteers not wearing a visor could get
    infected this way.
  • Contact – coming into contact with contaminated surfaces that have been sneezed on and then touching mouth/eyes/nose. Because of the frequent hand and surface washing, none of the volunteers should get infected this way.

By comparing the number of healthy volunteers infected the between the two groups it’s then possible to calculate the contribution of aerosols and droplets in the spread of flu.

Unfortunately we don’t know the results of the research yet, but when we do it could change the sorts of protective equipment used to look after patients infected during a flu outbreak. If the aerosol route turns out to be important then doctors and nurses will be given a respirator to wear when looking after a sick patient. I’m looking forward to reading about what Prof Van-Tam and his team find, and it’s certainly one of the more interesting experiments I’ve seen on flu for a while!

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