Coronavirus disease (COVID-19) is an infectious disease caused by a respiratory pathogen called the coronavirus, SARS-CoV-2. People who are infected with COVID-19 tend to experience mild to moderate respiratory disease and will recover without any special treatment being required. Some individuals who are infected will be asymptomatic, but majority of them would experience mild Covid-19 symptoms and recover on their own. Elderly people, especially those with underlying medical problems such as cardiovascular disease, chronic respiratory disease, diabetes, and cancer are more likely to develop severe complications.
How Long Does It Take After Exposure To Coronavirus For A Test To Detect It?
Infection with the virus (SARS-CoV-2) causing COVID-19 is confirmed by the presence of viral RNA which is detected by molecular testing, usually RT-PCR. The RNA of SARS-CoV-2 is detected in patients one to three days before the presence of symptoms, and the amount of viral load in the upper respiratory tract peaks within the first week of infection, followed by a gradual decrease over time.
How Long Are You Infectious When You Have Coronavirus Infection?
The interval between being exposed to the virus and the onset of symptoms is the "incubation period." The incubation phase for COVID-19 varies from one to 14 days, but most individuals tend to develop COVID-19 symptoms after three to six days of exposure to the virus. Recent research shows that people might potentially be more likely to transmit the virus to others within the first 48 hours before Covid-19 symptoms begin to develop. The duration and onset of COVID-19 viral shedding and the cycle of infectiousness are not yet known with certainty. Scientists believe, based on current evidence, that people with mild to moderate COVID-19 may shed replication-competent SARS-CoV-2 for up to ten days after onset of symptoms, while a small fraction of people with extreme COVID-19, including immunocompromised individuals, may shed replication-competent viruses for up to 20 days.
Detection of viral RNA does not necessarily mean that a person is infectious and will be able to transmit the virus to another person. Factors that determine the virus transmission risk include whether a virus is still replication-competent, whether the patient has symptoms, such as a cough & flu which can spread infectious droplets, and the behaviour and environmental factors associated with the infected person. The infected individual will gradually produce neutralising antibodies within five to ten days after infection with SARS-CoV-2.
When Is It Safe To Be Around Someone Who Has Recovered From Covid-19?
It is safe to be around the infected person after:
- ten days since symptoms first appeared and
- 24 hours with no fever and without the use of fever-reducing medications and
- Other Covid-19 symptoms are improving
Most people infected with coronavirus who have symptoms will no longer be contagious by ten days after symptoms resolve. People who tested positive for the virus but did not develop symptoms over the following ten days after Covid-19 testing are probably no longer contagious, but again there are documented exceptions. Thus, some experts are still recommending 14 days of isolation.
Please take note that these recommendations do not apply to persons with severe COVID-19 or with severely weakened immune systems (immunocompromised). People who are severely ill with COVID-19 might have to stay home longer than ten days and can extend up to 20 days after symptoms first appeared. Persons who are severely immunocompromised may need to do testing to determine when they can be around others.
Does The Presence Of Covid-19 Antibodies Mean A Person Is Immune And Safe From Being Infected Again?
The body responds instantly with a non-specific innate response to a viral infection in which neutrophils, macrophages and dendritic cells prevent the individual from producing symptoms by slowing down the progress of the virus. This non-specific innate response is followed by an adaptive response where the body makes antibodies that specifically bind to the virus. The adaptive immune response Involves two types of white blood cells known as T cells and B cells. The T cells can identify cells that are infected with a particular virus and increase in number rapidly to resolve the infection. The B cells will generate antibodies unique to the virus.
- IgM antibodies are first produced and disappear after a couple of weeks.
- IgG antibodies are formed at the same time or two to three days later. They usually stay for months or years
T cells and B cells decrease in number once the infection is over, but some cells can remain as memory cells. Memory cells react quickly if they come into contact again with the same virus, killing the virus and accelerating an antibody response. This whole process of immunity development to a pathogen will take one to three weeks.
Generally, a person who recovers from a viral infection is protected against a new infection, if the neutralising antibodies are of adequate quality and high level in quantity. Changes in the sequence of virus can make prior immunity to become less effective. Antigen stability is also involved where over time, viruses can mutate. Viral proteins can change such that even if they come into contact with the virus, antibodies generated against the virus will not recognise the antigens. A weaker innate response may result in delayed activation of the adaptive response in elderly people with underlying health problems or immunocompromised patients. Patients who have had more severe Covid-19 disease appear to have higher levels of neutralising antibodies while patients who was asymptomatic or had mild Covid-19 infections have low levels of neutralising antibodies or even undetectable levels of antibodies. Latest studies have shown that neutralising antibodies can disappear after three months. There is currently insufficient information to conclude whether people who have recovered from COVID-19 and have developed antibodies are protected from a second infection.
Should You Get Tested Again Before Returning To The Community?
At present, it is not advised to re-test people who have experienced mild illness, and have recovered from COVID-19. In order to return to the community, generally a person is considered safe and discontinue self-isolation if they are no longer infectious. This means that they developed their first symptoms more than ten days ago and for at least three days (72 hours) they did not have any symptoms.
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For More Information On Covid-19, Visit:
National Centre for Infectious Diseases
Centers for Disease Control and Prevention
Updated on 12 January 2021 by CaregiverAsia.
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