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The epidemiology of the SARS-CoV-2 virus - what we know and what we know we don’t know

What we already know

Key inputs about the virus are still too uncertain to be able to reliably model the path ahead	Given a wide rangę of possible values for key inputs, such as total number of infections or Case Fatality Ratę (CFR), the confidence intervals from any models remain wide. When R, is Iow, such as during lockdown, this is less important, but as restrictions relax the level of uncertainty around futurę outcomes increases
Reaching herd immunity is unlikely to be achievable without a significant number of deaths	The current number of deaths observed across affected countries, and the likely rangę for the CFR, suggests that reaching herd immunity would take time and kill many morę people.

Without widespread testing or statistically significant studies on unbiased samples. an accurate assessment of the number of people infected and recovered is lacking. Recent surveys in Heinsberg, Germany, have suggested national infection rates of c.2%, 10 times higher than the confirmed number of cases. A New York study of 15,000 people has suggested that c.12% had been infected._

There remain a wide rangę of estimates for the number of people infected and recovered

Further detail page 9

The CFR observed during contained outbreaks on cruise ships and aircraft carriers give a wide rangę of 0% to almost 2%. Recent studies from China and Germany conclude that the CFR is lower than 1%, but a precise value has not yet been established.

The CFR of COVID-19 is estimated to be below 1%, but a precise value has not yet been established

The WHO has stated that there is currently no evidence that people who have recovered from    Whether immunity lasts for those

COVID-19 are protected from second infection. The propensity of positive test results arising from    who have reCOVered from the

dead lung cells has madę it difficult to understand whether, when and how immunity might arise.    virus is not yet known

What we don’t know yet

Further detail page 10

The per capita death ratę for BAME people in the U.K. is observed at around twice that of white people. While some of this may be explained by socio-economic factors and the proportion of frontline workers, there may be medical reasons for this which are not yet understood.

The reasons why the virus seems to affect certain population sub-groups morę severely than others are unknown

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