Stop it, you're scaring me
What is the single most useful metric in measuring the spread of Swine Flu? I'm no doctor but I would think the most important metric would be the number of people who have Swine Flu. The media seem to agree. The main number being thrown around is the number confirmed cases of Swine Flu.
So how many confirmed cases of Swine flu are there in New Zealand right now?
"The number of confirmed cases of swine flu has risen to 86, an increase of 15 from yesterday, Health Minister Tony Ryall said today." - Stuff.co.nz
This means that 86 people in New Zealand have Swine Flu right? Not quite. Stuff got that information from the latest bulletin released by the Ministry of Health. Here's a direct quote from that bulletin:
"The cumulative total of confirmed cases in New Zealand is now 86 up from 71 yesterday. Of these, 66 are current cases being treated in isolation." - Ministry of Health
Stuff chose to only mention the cumulative total rather than the number of current cases. The 20 people who Stuff counts as cases but do not currently have Swine Flu are those who were infected but have now recovered (no deaths in NZ at this point). This number that the media keep touting, which increases every day, is the total number of Swine Flu cases in New Zealand ever. Not the number of people currently infected.
This becomes even more deceptive when the media emphasises the increase in cases. In an epidemic, the number of people infected starts of small, then it increases until at some point it peaks, then it decreases again. I don't need a medical degree to work that out. So in a very general sense an epidemic would look like a bell curve.
Do you see the problem yet? The media are reporting the number of cumulative cases instead of current cases. Instead of a bell curve this would graph as a constantly (but not steadily) increasing line. The number of cases is always increasing. Even when the epidemic is almost over, the number of cases is still increasing!
As I said earlier, I don't have a medical degree, but cumulative cases seems a ridiculous metric to use to measure the current threat posed by Swine Flu. It's deceptive and it feels like scaremongering. Please stop it.
Disclaimer: I'm not a doctor, I know nothing about epidemics, don't take me too seriously.
