The majority of people who get COVID-19 will be asymptomatic or have mild symptoms only.
Excellent new data from Remuzzi et al. in the Lancet
“The mean age of those who died in Italy was 81 years and more than two-thirds of these patients had diabetes, cardiovascular diseases, or cancer, or were former smokers. It is therefore true that these patients had underlying health conditions, but it is also worth noting that they had acute respiratory distress syndrome (ARDS) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia, needed respiratory support, and would not have died otherwise. Of the patients who died, 42·2% were aged 80–89 years, 32·4% were aged 70–79 years, 8·4% were aged 60–69 years, and 2·8% were aged 50–59 years (those aged >90 years made up 14·1%). The male to female ratio is 80% to 20% with an older median age for women (83·4 years for women vs 79·9 years for men).”
In other words, the majority of people who get COVID-19 will be asymptomatic or have mild symptoms only. From a public health perspective, the interesting take away for me from the data on Italy (which is consistent with the data from China) is that of those that died, most were elderly with underlying medical conditions who required hospital acute care. The authors thus call on the Italian authorities to urgently allocate resources for intensive care facilities.
Please note this does not mean all elderly people with underlying conditions who get the virus will require acute hospital care. With more data we will be better able to understand the so called “adjusted rates” which will help us better understand true risk factors and target prevention and care efforts to those at most risk.
Also, because we are not yet doing population-based surveillance testing, we don’t know how many people have already been infected. It is clearly many more than being reported as most people are asymptomatic or have mild symptoms that are similar to other illnesses. This is positive news – as it means the actual morbidity and mortality rates (e.g. risk of getting ill or dying if you are infected) will be lower (if the denominator is bigger and the numerator is the same – the rate is lower) including among the elderly and vulnerable.
The rationale for the mitigation strategy currently underway in NYC and elsewhere of “social distancing” is less about our own individual risk and more about trying to reduce the speed of transmission in the general population with the aim to reduce the speed of transmission in the elderly and vulnerable, some of whom may be at risk for requiring intensive hospital care which does not currently have a great deal of excess capacity. This strategy is being termed “flattening the curve” (e.g. not necessarily reducing the overall number of cases but trying to spread potentially acute cases over time) so the hospital system is better prepared and equipped to handle those that may need acute care (e.g. including proper respiratory care).