# Confused about a COVID reporting stat

What does Rt value mean? And what is R0?

Both mean Reproduction Rate. I believe they are used interchangeably.

It represents the number of new infections estimated to stem from a single case.

In other words, if R0 is 2.5, then one person with the disease is expected to infect, on average, 2.5 others.

An R0 below 1 suggests that the number of cases is shrinking, possibly allowing societies to open back up. An R0 above 1 indicates that the number of cases is growing, perhaps necessitating renewed lockdowns or other measures.

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This is a really interesting question so I looked it up.
I think @darkmite2 is right about R0, as far as I could tell the only difference between it and Rt is that Rt is more geographically and temporally narrow. I guess you could say Rt is a very specific R0.

Here’s a neat real-time chart that shows the Rt in any given state in the US.

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So, yesterday, my area had an Rt of .86. Today, it’s 1. That’s bad for us, right?

But right next door to us and even closer to the mega-city than we are, where we shop and interact, their Rt is .73, down from yesterday.

I guess the numbers are based on the counts of the day and maybe fluctuate easily, but it’s discouraging.

Going up from 0.86 to 1 is bad, but I’d guess the daily numbers, particularly for a small population, are incredibly noisy. I’d look more at a 7 day rolling average, if available, to see if things are getting better or worse as the numbers should be a lot less noisy. 'Course you need to wait awhile for the updated numbers…

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This is us for the last week:

One distinction I’ve read is the R0 is the reproduction rate absent any interventions or mitigating factors. R0 for a given virus strain does not change (absent mutation). R (without the naught) is the reproduction rate including the impact of any interventions. R can vary by location and time due to implementation and removal of measures.

Rt I assume is R at a given place and time?

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Oh dear, here in Mexico we barely gave number of deceased… and we can’t even get that right! I’d panic with these metrics!

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