Blog Articles


18 December 2020

What is COVID-19?

The new coronavirus, named SARS-CoV-2, causes the disease COVID-19. This virus was recently identified in December 2019 in the city of Wuhan, China.

Coronaviruses are a family of viruses that cause disease in humans. The infection can be similar to a common flu syndrome or present itself as a more serious illness, such as pneumonia, especially in the elderly or the immunosuppressed.

In the last decade, two new coronaviruses have proven to be highly pathogenic to humans: SARS-CoV, which was identified in 2002 as the etiologic agent of the Severe Acute Respiratory Syndrome (SARS) epidemic, and MERS-CoV, which was identified in 2012 as the etiologic agent of Middle East Respiratory Syndrome (MERS). Both SARS-CoV and MERS-CoV have zoonotic origin, that is, their natural reservoir is animals.

After carrying out several genetic studies, it was found that this new coronavirus belongs to the same group as SARS-CoV, identified in 2002. For this reason, the initial designation 2019-nCoV has been replaced by SARS-CoV-2, that is, the second coronavirus in the group that causes Severe Acute Respiratory Syndrome (SARS).

How is COVID-19 transmitted?

Transmission can occur from person-to-person by air (droplets> 5 microns) or by direct contact with infectious surfaces and/or secretions.

What are the symptoms of COVID-19?

The symptoms of COVID-19 appear 2 to 14 days after exposure to the virus and, in most cases, include:

Most patients with COVID-19 have mild or moderate symptoms. However, some people are asymptomatic, that is, they have no symptoms.

It is important to emphasize that patients without any symptoms, but who are infected, can also transmit the virus.

How is COVID-19 diagnosed?

[1] The RT-PCR methodology has a very high sensitivity (93%) and specificity (96%), which may reveal a positive result before the infected person has symptoms. This technique requires specialized personnel and equipment.

During the infection, it allows monitoring of the infection, since when the person is cured and does not have the active virus, the result must be negative.

What are the risk groups for COVID-19?

  • The elderly;
  • Chronic patients – Heart and lung disease, diabetes, neoplasms or arterial hypertension, among others;
  • Immunosuppressed people who are undergoing chemotherapy treatments, treatments for autoimmune diseases (rheumatoid arthritis, lupus, multiple sclerosis or some inflammatory bowel diseases), HIV or transplant patients.

Who should perform the RT-PCR test?

Suspected cases of infection with the new coronavirus should be tested in the laboratory.

Users with symptoms compatible with COVID-19, such as fever, cough and/or difficulty breathing and/or if they have been in contact with a confirmed case of COVID-19, must remain in prophylactic isolation at home. If the symptoms persist or the clinical condition worsens, you should contact the 24-hour ‘Saúde 24’ telephone line (808 24 24 24).

After contacting ‘Saúde 24’, you should follow the instructions given by the health professional, who will determine if it will be necessary to perform the COVID-19 test.

The test is not recommended for the general population without symptoms, since, during the virus incubation period, the viral load can be very low, and it is not possible to detect the virus and consequently give a false negative result.

If I tested positive for COVID-19, when can I get out of isolation?

If the RT-PCR test is positive for SARS-CoV-2, it indicates the presence of viral RNA, that is, that the person is infected.

If you have tested positive for COVID-19, you can only leave isolation when you have no symptoms and have 2 negative tests, with an interval of 24 hours.

If I tested negative for COVID-19, does it mean that I don’t need to take the necessary precautions?

If you tested negative for COVID-19, it means that, at the time you performed the test, no genetic material from the virus was detected. However, this does not mean that you cannot be infected, since, at the initial stage of infection, the test may still be negative.

In addition, if the test is negative, it does not imply that you should not take precautions, as you can be infected if you do not take them.

Why can there be false negatives in RT-PCR?

There are several reasons why the RT-PCR test may be negative, namely:

  • The amount of virus present in the sample is reduced, making it not possible to amplify and detect the virus;
  • Sample type, since the viral load in the upper respiratory tract is lower than that of the lower respiratory tract in COVID-19 patients;
  • Sample collection procedure;
  • Contamination in sample processing;
  • Inhibition of the RT-PCR reaction;
  • Failure to extract genetic material from the virus;
  • Cross reaction with other viruses.

How to make the appointment for the COVID-19 test?

Appointments for the test must be made via telephone or email to the AQUALAB Central Laboratory.

  • Albufeira — 289 580 890
  • Portimão – 282 424 250
  • Faro Moduslab: 289 889 590

Users should not go to the collection points or laboratory without prior notice.

Research of anti-SARS-CoV-2 IgM and IgG antibodies

In AQUALAB, serological tests can be carried out to search for anti-SARS-CoV-2 IgM and IgG antibodies, determining whether the person was previously infected or not, and to assess their immunity to the virus.

Serological tests allow determining the infection rate through epidemiological studies, assessing the degree of exposure of individuals to the virus and which individuals have developed antibodies to the new coronavirus.

The serological test performed at AQUALAB is a chemiluminescence immunoassay. This methodology allows the quantification of IgM and IgG antibodies for SARS-CoV-2.

To carry out this analysis, a medical prescription is not necessary, it is only necessary to go to an AQUALAB harvest station to carry out the analysis.

Who should perform the serological test?

  • People who presented a clinical condition compatible with COVID-19 infection but did not perform the RT-PCR test;
  • People who have been in contact with COVID-19 positive patients, have no symptoms and want to evaluate a possible immune response;
  • People who tested positive for COVID-19 and want to assess their immune response after infection;
  • Health care professionals, in order to determine the risk of exposure or inadvertent spread of the virus.

What information can the combination of RT-PCR and antibody detection give us?

For the diagnosis of acute infection, a molecular test such as RT-PCR must be performed, which detects the presence of the genetic material of the etiologic agent. The RT-PCR indicates who is infected at the time of collecting the sample.

Serological tests detect the presence of antibodies in the blood in response to a specific infection, such as COVID-19. These tests allow the detection of subclinical infections, preventing the spread of the virus.

The detection of antibodies, especially IgM, which are produced at the beginning of the infection, can be combined with RT-PCR to increase sensitivity.

Antibody kinetics

The sensitivity of serological tests depends on the stage and severity of the disease, being less specific than RT-PCR.

In the initial period of infection, antibody levels may not be detected, as the immune response is still being built. Each patient has a different antibody kinetics for antibody production.

The immune system produces IgM class antibodies at an early stage of infection, and IgG class antibodies are generated later. IgG persists in the body for a longer period than IgM, contributing to long-term immunity, which allows the immune system to quickly identify and respond to future infections by the same pathogen.

IgM appears approximately from 7 to 10 days after the onset of infection and persists in sufficient quantity for a few days, suffering a rapid decline after this period. IgG appears, on average, 17 days after infection by SARS-CoV-2 and persists for at least 49 days, according to scientific articles.

Currently, the scientific studies carried out do not allow us to know how long the IgM or IgG antibodies remain in the body after infection, that is, whether the immunity is transient or not.

Adapted from: MicroBIO Blog – News and curiosities about viruses, bacteria and microbiology

Adapted from: Ministry of Health – Interpretation of diagnostic problems against SARS-CoV-2 (April 24, 2020. Version 2)

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