What is the relationship between asymptomatic patients and the spread of covid-19?magazine JAMA network is open An analytical model was collected that pointed out how transmission among asymptomatic people represents more than half of all cases.
As Coronavirus disease Began to spread around the world. Scientists have observed that unlike the coronavirus that caused the 2003 outbreak, SARS-CoV-2 It cannot be stopped through symptom screening alone.
according to Scientific publications In the 2003 SARS-CoV, asymptomatic infection And clinically mildly rare.Besides, there is nothing spread Before the onset of symptoms. However, the new coronavirus spreads faster than the old coronavirus, and tests have shown that it is indeed spread from people who have no symptoms.
What is still known exactly is the proportion of COVID-19 infections associated with these patients.magazine JAMA network is open Just released survey Point out that the transmission of asymptomatic people accounted for more than half of all cases.
Its author, a scientist at the Centers for Disease Control and Prevention (CDC), the statement from Atlanta, USA stated that only the identification and isolation of individuals with symptoms of covid-19 will not be able to control the current spread of SARS-CoV-2.
Symptom-based testing will never control transmission. Jay C. Butler explained that the use of masks outside the home should be adopted in everyone’s home to avoid crowding and distance from others, until the higher population can be achieved through the use of safe vaccines and effective methods. Immunity so far. , One of the authors, Sinc.
The transmission of infected but asymptomatic people can originate from two different infection states: symptomatic people (contagious before symptoms appear) and people who have never experienced symptoms (asymptomatic or asymptomatic infections) .
Experts analyzed the proportion of transmission and the period of infection among people who have never experienced symptoms (that is, remain asymptomatic) under different conditions. The relative infections of asymptomatic and symptomatic patients before symptoms vary according to the best published estimates degree.
The importance of people without symptoms
The basic assumption of the model is that the greatest infectivity occurs at the median symptom onset, 30% of infected people never show symptoms, and 75% of infectivity is the same as those who have symptoms. Taken together, these baseline assumptions mean that infected individuals who have never developed symptoms may account for approximately 24% of all transmissions.
So the result shows 59% According to the baseline situation of the model, the vast majority of all transmission comes from asymptomatic transmission. on the other hand, 35% How many of the new cases are people who infect others (symptomatic individuals) before the onset of symptoms; and twenty four%, People who never show symptoms.
Scientists from the Centers for Disease Control and Prevention said: “Within the broad range of values of each hypothesis, it is estimated that at least 50% of new SARS-CoV-2 infections originate from individuals exposed to infections but asymptomatic. ”
The authors guarantee that in addition to identifying and quarantining people with symptoms of COVID-19, to effectively control transmission, the risk of transmission from asymptomatic infected people must also be reduced.
“Use something like maskThey concluded that until there is no safe and effective vaccine and widespread use, hand hygiene, social distancing and strategic testing of those who are not sick will continue to be essential to slow the spread of the disease.
Jay C. Butler and others: SARS-CoV-2 transmission in people without COVID-19 symptoms. JAMA Cyber Open 2021; 4(1): e2035057. doi: 10.1001 / jamanetworkopen.2020.35057