I’m no expert, but I dug up some information while trying to understand the claims that the virus has “peaked” in Hubei. I think there’s some information in the links I’m adding that is important enough for anyone wanting to understand the life cycle (or waves) of an epidemic or pandemic to read through.
Before I get started on the “waves”, I want to give a quick OPINION on the wave cycle of COVID-19. I believe the time to be on highest alert with this virus is immediately following the identification of the FIRST CONFIRMED COMMUNITY DIAGNOSIS IN YOUR AREA! COVID-19 has proven that it is very stealth in nature. My opinion, when that first case is identified in your area, you’re in fact standing in the middle of the invisible wave. Read below and hopefully it will help explain my statement OF OPINION.
In trying to understand it, I started to think of it as a literal wave. Imagine, if you will, a large invisible tidal wave that sweeps across an area (or country). As it sweeps across a population, the initial impact will start to expand, with additional cases being identified every day after the initial cases. If it reaches an epidemic level, then the number of cases will continue to rise on a daily bases until it “peaks”. In regards to an epidemic, the peak is considered the day that has the highest total number of newly reported cases. Once the virus has “peaked”, that doesn’t necessarily mean the virus is actually going to fade away, but the number of daily new cases will either drop off, or will level out.
What’s really important to realize about the peak level is that the peak will occur either when the majority of the population has been infected OR when quarantine measures have an effect on the spread.
So, in regards to the “peak” in Hubei, it’s basically one of two things....
1) The majority of the population has already been infected and the majority had relatively mild symptoms, or
2) The quarantine lockdown has drastically reduced the spread.
Personally, I think #2 is more likely. And if that is the case, once the quarantine restrictions start to be eased, Hubei could see a second “wave”. Different things can cause waves... In regards to the flu, every flu season is basically a viral wave. And every flu wave has the potential to be considered an epidemic if it spreads fast enough or has a high enough mortality rate to meet the criteria.
I have more to add regarding the Hubei “peak”, but I’m looking for some links that I apparently misplaced.... too much info to keep up with
Pandemics: Past, present, and future
Understanding Epidemics: Section1B: The Epidemic Wave