As the COVID-19 outbreak continues to evolve via asymptomatic and symptomatic transmission routes, we are learning more about this new virus every day. Here we summarize what has been reported about transmission of the COVID-19 virus. We provide also a brief overview of available evidence on transmission from symptomatic, pre-symptomatic and asymptomatic people infected with COVID-19.
Are asymptomatic people spreading the coronavirus? A WHO top official joins the debate and answers. Maria Van Kerkhove notes that scientists have not determined yet how frequently people with asymptomatic cases of Covid-19 pass the disease on to others.
How does the coronavirus spread?
WHO’s technical lead on the Covid-19 pandemic had mentioned that such spread is “very rare. She added that people who didn’t show symptoms were unlikely to spread the virus. Maria Van Kerkhove mentioned that the actual rates of asymptomatic transmission aren’t yet known.
Asymptomatic spread is the transmission of the virus by people who do not have symptoms and will never get symptoms from their infection. But those infected carriers could still get others very sick.
The majority of transmission that we know about is that people who have symptoms transmit the virus to other people through infectious droplets. Van Kerkhove, World Health Organization
Pre-symptomatic spread is the transmission of the virus by people who don’t look or feel sick. These people will eventually get symptoms soon later.
“But there are a subset of people who don’t develop symptoms, and to truly understand how many people don’t have symptoms, we don’t actually have that answer yet” Van Kerkhove said. “We are constantly looking at this data and we’re trying to get more information from countries to truly answer this question” she added.
How is it possible to spread coronavirus without symptoms?
The coronavirus spreads from human to human via small droplets when coughing and sneezing. Via these droplets, the virus ends up in the air, on objects and surfaces. Whoever inhales these droplets or gets them through their hands into their mouth, nose or eyes can become infected with the virus. There is no evidence that the contamination occurs through the skin. The risk of infection is reduced by keeping more than a metre away from sick people, touching one’s face as little as possible and paying attention to good hand hygiene.
The routes of transmission from COVID-19 patients
What’s the difference?
By way of definition, a symptomatic COVID-19 case is a case who has developed signs and symptoms compatible with COVID-19 virus infection. Symptomatic transmission refers to transmission from a person while they are experiencing symptoms.
Data epidemiology and virologic studies provide evidence that COVID-19 is primarily pass from symptomatic people to others who are in close contact through respiratory droplets, by direct contact with infected persons, or by contact with contaminated objects and surfaces. This is supported by detailed experiences shared by technical partners via WHO global expert networks, and reports and presentations by Ministries of Health.
Data from clinical and virologic studies that have collected repeated biological samples from confirmed patients provide evidence that shedding of the COVID-19 virus is highest in upper respiratory tract (nose and throat) early in the course of the disease.8-11 That is, within the first 3 days from onset of symptoms. Preliminary data suggests that people may be more contagious around the time of symptom onset as compared to later on in the disease.
The incubation period for COVID-19, which is the time between exposure to the virus (becoming infected) and symptom onset, is on average 5-6 days, however can be up to 14 days. During this period, also known as the “presymptomatic” period, some infected persons can be contagious. Therefore, transmission from a pre-symptomatic case can occur before symptom onset.
In a small number of case reports and studies, pre-symptomatic transmission has been documented through contact tracing efforts and enhanced investigation of clusters of confirmed cases. Many medical data suggest that some people can test positive for COVID-19 from 1-3 days before they develop symptoms. Thus, it is possible that people infected with COVID-19 could transmit the virus before significant symptoms develop. It is important to recognize that pre-symptomatic transmission still requires the virus to be spread via infectious droplets or through touching contaminated surfaces.
An asymptomatic laboratory-confirmed case is a person infected with COVID-19 who does not develop symptoms. Asymptomatic transmission refers to transmission of the virus from a person, who does not develop symptoms. There are few reports of laboratory-confirmed cases who are truly asymptomatic, and to date, there has been no documented asymptomatic transmission. This does not exclude the possibility that it may occur. Asymptomatic cases have been reported as part of contact tracing efforts in some countries. WHO regularly monitors all emerging evidence about this critical topic and will provide an update as more information becomes available.
Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19
Estimating the extent of asymptomatic COVID-19
For COVID-19, data to date suggest that 80% of infections are mild or asymptomatic, 15% are severe infection, requiring oxygen and 5% are critical infections, requiring ventilation.
What happens when you get the coronavirus disease?
People with COVID-19 generally develop signs and symptoms, including mild respiratory symptoms and fever, on an average of 5-6 days after infection (mean incubation period 5-6 days, range 1-14 days). Most people infected with COVID-19 virus have mild disease and recover.
The coronavirus is a new and highly infectious virus. You can easily catch it from other people or pass it on to them. The virus can cause a range of symptoms, from ranging from mild illness to pneumonia. Symptoms of the disease are fever, cough, sore throat and headaches.
Asymptomatic transmission still an ‘open question’
Although for most people COVID-19 causes only mild illness, it can make some people very ill. More rarely, the disease can be fatal. Older people, and those with pre- existing medical conditions appear to be more vulnerable. These people have high blood pressure, heart problems or diabetes. You can recover from the coronavirus disease (COVID-19). Catching the new coronavirus DOES NOT mean you will have it for life. Most of the people who catch COVID-19 can recover and eliminate the virus from their bodies.
No-one has antibodies to make them immune to the virus. There is no vaccine at present either. Doctors and scientists are currently researching the virus. They are analysing every person who gets ill and learning more every day. This will help them find the right treatment. If you are ill but not in hospital, then paracetamol is the best medicine for pain and fever. Some criminal organisations are selling fake or illegal medicines containing chloroquine. There is absolutelyno guarantee that these medicines will be safe or work properly. They could even be very bad for your health, so you should not buy them.
Are children more at risk of being infected by asymptomatic transmission?
According to the data presently available, children play a limited role in the transmission of the coronavirus (in opposition to the influenza virus). They also have few risks of developing a severe form of the disease.
The European Commission is coordinating a common European response to the coronavirus outbreak. EU is taking resolute action to reinforce public health sectors and mitigate the socio-economic impact in the European Union. European Union is mobilising all available means to help Member States coordinate their national responses. EU provides objective information about the spread of the virus and effective efforts to contain it.
To kick-start the European recovery, protect lives, livelihoods and jobs, the European Commission is proposing a major €2,4 trillion recovery plan. This plan is based on using a powerful and modern EU budget to deliver a more sustainable, digital, and fair Europe. President von der Leyen said: “These investments will not only preserve the outstanding achievements of the last 70 years, but will also ensure that our Union is climate neutral, digital, social and a strong global player. This is Europe’s moment.”
We have been adapting our behaviour for our own health and that of others: increased hand hygiene, keeping a physical distance from other people, limiting non-essential contact and staying at home as much as possible, especially when presenting symptoms, and so on. By following all these measures, we are helping healthcare providers to manage this COVID-19 pandemic.
Face masks. I protect you, you protect me
Personal and professional activities will be gradually restarting, in a period where the coronavirus is still present in our society. We will have to adapt, without losing sight of the basic rules. Wearing a face mask will be an additional measure that will help us make this transition successful. Experts predict that covid-19 will spread more widely but the world is getting ready.
Wearing a face mask is not about protecting yourself, but rather about protecting others.