Covid-19 is a disease caused by SARS-CoV-2. SARS-CoV-2 stands for Severe Acute Respiratory Syndrome Coronavirus 2. SARS-CoV-2 will be shortened to SARS-2 for easier reading in this article.
A previous article, The SARS-CoV-2, is still present after Covid-19 described how virus particles are continually being shed by a patient that had recovered from the illness. Virus particles are bits of ribonucleic acid that makes up the SARS-2. It is used to detect the presence of the virus.
This brings out a question. Are viral particles infectious?
An unpublished German study in MedRxiv, Virological assessment of hospitalized cases of coronavirus disease 2019, provides us an answer. It is new research that is not yet published in a peer-reviewed journal.
Ideally, scientific studies must be looked at by other scientists to see if the research method is sound. Well done researches make meaningful results.
However, in the face of a rapidly spreading virus, any information may be of help to explain the new illness.
The majority of Covid-19 or SARS-2 cases are mild (80%). They are usually instructed to stay home or self-quarantine for two weeks. At the end of the quarantine, testing of the nose and throat are done to make sure that there are no more SARS-2. The findings of this study support that the duration of quarantine and other noteworthy results.
How did they do it?
They tested nine people with mild Covid-19 symptoms. Their nasal passages, throat, and sputum were tested for the number of viruses from the first day that they were sick until they have recovered from the illness. The antibody levels against the SARS-2 were measured as a sign of recovery from the disease. Antibodies are produced in response to an infection.
What did they discover?
The findings support that Covid-19 is much more infectious than SARS.
SARS caused an outbreak in 2002-2003 and resulted in more than 8,000 cases. The current Covid-19 pandemic has resulted in more than 129 thousand cases and 4,700 deaths as of this writing. In the study, several features of the SARS-2 explains the wider spread.
The SARS-2 can multiply in the upper and lower respiratory tract. The SARS virus only grows in the lungs. The SARS-2 virus was detected on the nose and throat on the first day of the symptoms. As coughing starts, the SARS-2 spreads. The symptoms can be confused with other viral infections, and which makes it hard to sort out from other viruses like the flu.
The rate of multiplication of the SARS-2 peaked before day 5 of the symptoms and is 1000 times higher than SARS. At the onset of mild symptoms, the SARS-2 is already infectious. 
What is the course of mild Covid-19?
The patients included in the study have mild symptoms. Mild cases usually do not require hospitalization.
To illustrate the course of the virus in them, let us say that the first day of symptoms (cough, fever, and runny nose) is Day 1. The scientists counted the number of SARS-2 viruses every day in the nose, throat, sputum, and stools. They found a rapid rate of multiplication during the first five days of illness, and then it slows down.
After day 10 of symptoms, the SARS-2 becomes undetectable in the majority of cases. For two patients who later developed signs of pneumonia, the virus continued to multiply and shed even after day 10.
Mild cases start to develop antibodies quickly. Typically within six to 12 days. Antibodies are produced by the body to fight the infection. The rapid increase of the antibodies may explain why most Covid-19 cases are mild (80% of cases).
No virus found in the blood and urine and stool.
- The blood and urine did not show any virus.
- They were not able to detect any live virus in the stools. However, the stools were collected from patients with mild diarrhea. Based on the stool findings, the authors believe that respiratory transmission more of a concern than fomite transmission.
Addendum 3/13/2020. A Research letter was written to the CDC that showed a study where they can extract the virus from 29% of stool samples.
Take away message
The most significant finding in this study is the absence of the SARS-2 virus after 10 days of no symptoms after the infection. This study supports the 14-day duration of quarantine that is currently recommended and the testing needed before a patient can be released from quarantine.
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- The Covid-19 can Attack the Brain
- New Study Explains the Rapid Spread of Covid-19
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- Is the Covid-19 epidemic Fake News?
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Image credit:
SARS-CoV-2 By NIAID – https://www.flickr.com/photos/niaid/49557785797, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=87326871
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