If you mean RT-PCR, a positive test result for SARS-CoV-2 infection can be obtained with a throat swab in the first week of infection. If the case is suspected to have had the infection for a least a week, i.e. they are in the second week following the infection, pulmonary discharges, e.g. sputum, is preferred, as the virus can no longer be detected in throat in this time period.

https://covidreference.com/diagnosis

Hello!

It depends on the particular test. PCR tests detect active infections, they are highly specific and the sensitivity varies depending on how well the biochemistry is optimized. See here:

Article Variation in False-Negative Rate of Reverse Transcriptase Po...

Serological tests (antibodies or antigens) do not necessarily detect active infections but also previous episodes. They are much less specific than PCR tests.

Dear, Muhammad Ghafoor Ali

Normally, on average it takes 5–6 days from when someone being infected with the virus for symptoms of the COVID-19 to appear, however it can take up to 14 days. The minimum time required for detection of patient after infected with virus is depends on the particular test. In case of RT-PCR, a positive test result for COVID-19 infection can be obtained in the very first week of infection.

Thank you Mr. Shirvaliloo, Schneider and Bitu

Although RT-PCR test for COVID-19 on nasopharyngeal or oropharyngeal swabs usually is positive by 5th day of the illness, the positivity of the test depends on the quality of the sampling technique as well as by the sensitivity of the test kit. Therefore, in a patient with suggestive symptoms of COVID-19, if negative initially RT-PCR result may become positive on repeated testing on 6- days of the illness.

Hope there articles can illuminate you about this topic:

1. Article Real-time RT-PCR in COVID-19 detection: issues affecting the results

2. Article Diagnosis of the Coronavirus disease (COVID-19): rRT-PCR or CT?

3. Preprint Diagnosis of Coronavirus Disease 2019 (COVID-19): Neither Ch...

Thank you Prof. Yousuf for respond

The virus takes few days to be detectable in the current standard pcr based tests

But please remember, the virus takes similar or even more time to show symptoms...so there should be no delay in testing when symptomatic

It depends on the specific test. PCR tests detect active infections, they are very specific, and sensitivity varies depending on how well biochemistry is optimized. Normally determine the virus for 5-6 days. Test systems in China more accurate begin to determine on day 2 of infection. In Russia, the test systems of the "Vector" Corporation give a positive result from the first days of infection. Regards, Sergey Viktorovich Pushkin

Thank you Mr. Ish and Viktorovich

The PCR is the best test for detection of the acute infection by the COVID-19

Hello prof. Muhammad Ghafoor Ali

RT-PCR is the best method to diagnose an acute COVID-19 infection. specific antibodies Determined using serological tests are applied to check the abundance and period prevalence of the disease, but does not show active infection.

Only take few days (1-3) to become positive

Thank You Prof.Rodrigo and Turki

When the test for covid 19 become positive after infection of virus ,the development of immunity to a pathogen through natural infection is a multi-step process that typically takes place over 1-2 weeks.the body responds to a viral infection immediately with a non specific innate response in which macrophages ,neutrophils and dendritic cells glow the progress of virus and many even prevent it from causing symptoms.this non specific response is followed by an by an adaptive response where the body makes antibodies that specifically bind the virus.those antibodies are proteins called immunoglobulins.the body also makes T-cells that recognize and eliminate other cells infected with cells infected with the virus,this is called cellular immunity .this combined adaptive response may clear the virus from the body,and if the response is strong enough may prevent progression to severe illness or reinfection by the same virus.this process is often measured by the presence of antibodies in blood .

Who continues to review the evidence on antibody responses to SARS-cov 2 infection.most of these studies show that people who have recovered from infection have antibodies to the virus.However ,some of these people have very low levels of neutralizing antibidies in their blood ,suggesting that cellular immunity may also be critical for recovery .As of 24 April 2020 no study has evaluated whether the presence of antibodies to Sars cov2 confers immunity to sebsquent infection by the virus in humans.

Laboratory tests that detect antibodies to sars cov 2 in people including rapid immuno diagnostic tests,need further validation to determine their accuracy and reliability.inaccurate immunodiagnostic tests may falsely categorize people in 2 ways the first is that they may falsely label people who have been infected as a negative and the second is that people who have not been infected are falsely labelled as positive both errors have a serious consequences and will affect control efforts .these tests also need to accurately distinguished between past infections from sars cov2 and those caused by the known set of six human coronavirus.four of these viruses causes the common cold and circulate widely.

These studies will provide data on the percentage of people with detectable covid 19 antibodies ,but most are not designed to determine whether those are immune to secondary infections,there is not enough evidence about the effectiveness of antibodies mediated immunity to guarantee the accuracy of an "immunity passport "or "risk free certificate .people who assume that they are immune to a secondary infection because they have received a positive test result may ignore public health advise.

Hello Prof. Ali

Most scientific articles emphasize of 5-7 days.

Thank you Prof.Judith

Thank you Prof.Turki

A mayor factor is that african population is much younger - 41% below 15 years means the virus will spread not as fast and only 3% 65 and older (Italy for instance is well over 20%) may get the case-fatality-rate down. Of course extremly low levels of testing are also a mayor factor for the numbers.

Thank you Prof.Ziemendorff

The virus becomes detectable after 5-14 days. The incubation period is quite long. There are different test systems. But this, as a rule, does not allow to detect the virus, for example, for 1 day of infection. Regards, Sergey Viktorovich Pushkin

Thank you prof. Viktorovich

The response rate is slowed and needs 1-2 weeks to become clearly positive

It is very difficult to predict for an assymtomatic pateints who are actively spreading infections . The nature of Covid mutation also plays a role between

Lag ( Inactive ) to Exponential Phase ( Symptomatic Covid pateints ).

Patient will start having symptoms with covid 19 between 2-14 days,this symotoms appears after exposure,the symptoms include tiredness,sore throat,headache,diarrhea,chills,cough,muscles ache,body pain etc

Thank you Prof. Rodrigo, Datta and Judith

Around 7 to 14 days in general, but again, it depends on the individual

Thank you Prof. Michael Halim

is positive few days after the infection and its duration is about 3 weeks

It is different from one to another, but generally began in 1-2 week after symptoms appear.

Thank you Prof. Luis Rodrigo

Thank you Prof. Hasan Falah Lahij

Minimum 4-5 days. Before this time, report will come negative.

Thank you Prof. Sagar Banik