New Year's Wish Granted: Signs of lower epidemic severity emerge in the Omicron wave in Melbourne

Near The Peak?

Previous Pundit posts have flagged some hopeful signs of lower disease severity in the nasty COVID-19 epidemic raging in Sydney Australia.

The epidemic Omicron wave in the sister city, Melbourne, started a little later than Sydney’s wave, so signals of lower epidemic severity were slower to emerge.

There are now some hopeful signs that lower disease severity is showing up in the Melbourne outbreak.

This shift in severity is expected from the behaviour of the Omicron wave in several other countries but its nice to see it in your home town.

Here is a graph showing current epidemic behaviour in the state of Victoria where Melbourne is located.

The blue curve is reported diagnosed coronavirus infections each day. The orange curve is the corresponding number of hospitalised patients (adjusted for the 5-day lag between symptoms and transfer to hospital for severely ill patients).

Both curves are plotted on a log scale. There is an upturn in both blue and orange curves at the start of 2022 — at the time of the wave of infection with Omicron virus variant.

Also plotted on the graph is the gap between the two curves just mentioned (i.e the difference log (cases) -log (hospitalisation). This is related to the case/hospital number ratio and is a good index of disease severity, with higher values meaning relatively less severe disease.

The index takes an upturn early January, (see red arrow on graphic), meaning that if you get infected chances of needing hospital care are lower with this latest wave than the preceding Delta wave.

Assuming the index remains constant in the week ahead, we can predict future expected hospitalisation. Hospital numbers may well peak near 5000 if daily cases have now reached their highest number, based on this projected trajectory shown in grey on the graph.

If the index of severity improves further, future hospital numbers will be lower still. Let’s hope that happens.

Most importantly, let’s hope both epidemic infection transmission halts very soon, as huge numbers of infections swamp out any benefits from any lower intrinsic severity of the Omicron virus.