What is COVID-19 pandemic? Symptoms Diagnosis and Precautions

What are the symptoms of covid 19 in humans

What is COVID-19 pandemic?

Coronavirus Infection, also known as coronavirus disease 2019 (COVID-19) is an emerging zoonotic viral respiratory infection caused by the 2019 novel coronavirus (2019-nCoV, SARS-CoV-2 virus), an enveloped positive-sense single-stranded RNA (ssRNA+) virus that belongs to the order Nidovirales in the subfamily Coronavirinae.

After becoming infected with the 2019 novel coronavirus (2019-nCoV), the virus will most likely remain in the body for life, lying dormant in the salivary glands (submandibular and sublingual glands).[1] In most confirmed cases, SARS-CoV-2 was detected at high titers in the salivary glands (submaxillary salivary glands).

Can covid 19 be transmitted through salivary droplets?

SARS-CoV-2 is present in salivary or nasopharyngeal secretions of patients who are diagnosed with COVID-19 (high viral loads in saliva), which is why salivary droplets play a critical role in viral transmission!

ACE2+ (angiotensin-converting enzyme 2-positive) cells are widely distributed in the upper respiratory tract, and especially in salivary gland duct epithelium (the epithelial cells lining salivary gland ducts), these ACE2+ cells are early target cells of the 2019 novel coronavirus (2019-nCoV) that can be productively infected.

The 2019 Novel Coronavirus (2019-nCoV) relies on the host cell for replication. An active replication of the viral genome results in a lytic phase of replication, in which, virus progeny are released into the environment to find and infect new cells, often after host cell is exhausted of all resources (upon the lysis of the host cell). The ability to move from latent to lytic infections and vice versa helps the 2019 Novel Coronavirus spread from infected individuals to uninfected individuals.

Where is the coronavirus found?

The 2019 novel coronavirus (2019-nCoV) epidemic outbreak started in December 2019 in Wuhan, the capital of Hubei, China

Is COVID-19 a deadly disease?

Coronavirus disease 2019 (COVID-19) is a viral respiratory illness that was first reported in China, in December 2019. Symptoms are those of an acute respiratory illness, similar to severe interstitial lung disease, or pneumonia. There is currently no vaccine or cure for COVID-19, and so far it has been fatal in around 3% of cases.

Can you die from COVID-19?

About 3 percent of patients who were diagnosed with COVID-19 have died. While COVID-19 is predominantly a silent disease, it can be deadly. As of 27 February 2020, a total of 82,586 confirmed cases and 2770 deaths from COVID-19 have been reported to the WHO since 2019, by 49 countries. Acute respiratory distress, heart failure and kidney failure are three complications of a COVID-19 that can be fatal.

COVID-19 is also similar to MERS in that it is zoonotic, meaning it is transmitted from animals to humans.

As of 12 July 2020, a total of 12,552,765 confirmed cases and 561,617 deaths from COVID-19 have been reported to the WHO.[2]

Is COVID-19 contagious?

The 2019 Novel Coronavirus (2019-nCoV) that causes COVID-19 is contagious, but unfortunately COVID-19 is predominantly a silent disease, in most cases, symptoms generally appear within 14-35 days after exposure, the 2019-nCoV infection may at first have few or no symptoms, so you may not know you have Coronavirus disease 2019 (COVID-19). SARS-CoV-2 virus is transmitted by direct contact, healthcare workers treating 2019-nCoV-infected patients are at high risk.

Patients infected with the 2019 novel coronavirus (2019-nCoV) have spread SARS-CoV-2 to others in hospitals and other healthcare settings.

What are the symptoms of covid 19 in humans?

Symptoms of  COVID-19 may range from mild to severe. They include fever (≥37·3°C), cough, angina (chest pain), dyspnoea (about 3% of patients develop shortness of breath on admission), body aches (myalgia), fatigue. Less commonly, vomiting and diarrhea. Disease is usually very mild in kids and children and is more severe in senior patients with underlying diseases, such as diabetes, heart failure, chronic obstructive pulmonary disease (COPD), and HIV.

Infectivity and disease transmission

The genome of SARS-CoV-2 is about 29.7kb, it shares a highly similar genome sequence (SIN2500) with SARS-CoV. The SARS-CoV-2 virus has 13 known genes and 14 known proteins.

SARS-CoV-2 interacts with human and animal hosts and uses angiotensin-converting enzyme-2 (ACE2) as its host receptor to gain entry into the cells in order to infect them.

SARS-CoV-2 evolution in patients should be closely monitored for the emergence of novel mutations at a specific spot in its genome in order to predict the possibility of a more severe outbreak than has been seen so far.

The emergence of novel mutations at the 501 (or 494) position in the SARS-CoV-2 genome could significantly enhance its ability to bind with human ACE2.

How long does it take for a person to get infected with 2019-nCoV?

The incubation period for COVID-19 ranges from 14 to 30 days. COVID-19 is characterized by an acute onset, symptoms usually develop abruptly and progress quickly. Without proper supportive antiviral therapy, symptoms usually reach their peak within 3-4 days

How do you get 2019-nCoV? – Can asymptomatic patients transmit COVID-19?

The source of infection:

A person infected with the 2019 novel coronavirus (2019-nCoV) is always contagious. COVID-19 is caused by direct contact with an infected person or virus carrier. In most cases, 2019-nCoV is caught by direct contact with an infected person or animal.

How can 2019-nCoV be transmitted to humans?

In most cases, the 2019 novel coronavirus (2019-nCoV) spreads by respiration of contaminated airborne droplets when an infected person sneezes or coughs on you, or by close person-to-person contact with infected individuals, such as shaking hands, touching, hugging, kissing, contact with oral secretions, sexual contact, and sharing equipment and utensils (poor personal hygiene). Moreover, 2019-nCoV can also be transmitted through direct or indirect contact with infected animals in wet markets, restaurants, or homes. Less commonly, 2019-nCoV can spread by touching an object or surface contaminated with contaminated droplets

2019-nCoV pathogen can be transmitted through vertical transmission, and in breast milk

The 2019 novel coronavirus (2019-nCoV) can travel through the air, enveloped in tiny respiratory droplets (≤60 μm in diameter).

Respiratory droplets ≤5 μm have the potential to be inhaled into the bronchi and alveoli in the lungs (the lower respiratory tract).

In humans, these respiratory aerosols (droplets) are produced when we breathe, talk, sing, sneeze and cough, these naturally generated respiratory droplets (aerosols) are likely to vary in both size and content and may travel up to nine feet (~3 meters) from patients’ respiratory tracts; Moreover, SARS-CoV-2 can circulate through the air.

Contaminated respiratory droplets may stay suspended in air currents long enough to be transmitted over considerable distances >1 m. Large droplets (>60 μm in diameter) are transmitted only over a limited distance (e.g. ≤1 m)

Coronaviruses (CoV) are a large family of viruses that can last on surfaces, from hours to months.

Diagnosis / How to diagnose COVID-19

How do you get tested for COVID-19?

Specific diagnostic lab tests are used to detect viral RNA and antibody responses and to establish a cause in individuals suspected to have COVID-19

The early diagnosis of COVID-19 is critical to prevent the spread of COVID-19

To decide whether SARS-CoV-2 is present in your body, your doctor will obtain clinical specimens, such as sputum, nasopharyngeal aspirates, saliva, nose and throat swabs, endotracheal aspirates, urine, and faeces, to examine them in order to detect SARS-CoV-2-specific RNA. Moreover, SARS-CoV-2-specific RNA can also be detected by inoculating cell cultures and growing the SARS-CoV-2.

How soon can you get tested for COVID-19?

SARS-CoV-2-specific RNA can be detected in the first 5 days of illness in patients with suspected SARS-CoV-2 through RNA tests, serologic response, and viral culture.

Viral culture is only useful in the first three weeks of illness.

Detection rates of SARS-CoV-2 specific RNA peak at day 11 after onset of illness. However, SARS-CoV-2 specific RNA remains detectable in respiratory secretions, urine and stool specimens for more than 30 days after onset of illness

Nasopharyngeal aspirates, throat swabs, or sputum samples are the most useful clinical specimens in the first five days of illness. However, stool specimens can also be used to detect SARS-CoV-2 specific RNA later in the illness

Serum specimens are collected to test for antibodies to SARS-CoV-2 and to detect SARS-CoV-2 in patients with COVID-19, respectively, whereas, throat and faecal swab specimens are collected and tested for SARS-CoV-2 RNA

Paired serum samples are collected to detect antibody response to SARS-CoV-2

What tests are used to diagnose COVID-19 infection?

Specific laboratory tests are used to detect SARS-CoV-2 RNA and antibody responses in patients suspected to have COVID-19

Tests include:

The COVID-19 RT-PCR test, a reverse transcriptase polymerase chain reaction, and indirect immunofluorescence (IFA) serological test for SARS-CoV-2

Reverse-transcriptase polymerase chain reaction (The COVID-19 RT-PCR test) is the gold standard test for detecting SARS CoV-2 RNA.

The specificity and sensitivity of the Real-time PCR assays based on the LightCycler® technology have been confirmed. All PCR-positive stool specimens should be retested by the Roche LightCycler 480 II PCR

SARS-CoV-2 can also be detected using EIA (enzyme-linked immunoassays).

These tests are performed on respiratory secretions and serum specimens.

ELISA can also be used to detect antibody to SARS CoV-2

How to prevent covid 19 in a simple way

Protect yourself and others around you by taking some simple precautions:

Stay at home if you feel unwell (self-quarantine for 14 days)

Practice social distancing, stay at home as much as you can and maintain a safe distance, stay at least 6 feet (about 2 meters) from other people, especially if they are coughing or sneezing

Maintain proper hygiene and sanitation, washing the body often with soap, washing the hair with shampoo/soap at least once a week, brushing your teeth with fluoride toothpaste at least once a day, put your outdoor clothes straight into the washing machine and wash using your usual laundry detergent

Wash your hands with soap and water for at least 20 seconds or use a disinfectant product containing 70% alcohol (an alcohol-based hand rub) before eating, or preparing food, and after sneezing, coughing, or blowing your nose

Cleaning and disinfecting your home or facility, clean high-touch hard surfaces with soap or detergent along with dettol antiseptic disinfectant liquid daily

Clean or sanitize grocery or consumer products once you get them home before usage or storage in your kitchen using a damp piece of cloth. Mix a teaspoon of clorox bleach liquid with three cups of water and three drops of dishwashing liquid in a bucket, toss in a piece of cloth and squeeze the cloth in your hand as hard as you possibly can, use this cloth to clean grocery products

Wear a mask when you go outside, especially when social or physical distancing is not possible

Cover your nose and mouth with a tissue when you cough or sneeze. If no tissue is available, cough or sneeze into your bent elbow, not your hand [3]

Sick? Seek medical attention


There is currently no cure for patients infected with the 2019 novel coronavirus (2019-nCoV)

If diagnostic tests fail to detect monoclonal antibodies to SARS-CoV-2 after three weeks from onset of illness, this means that no infection with the 2019 novel coronavirus (2019-nCoV) took place!

Asymptomatic (contact tracing) and symptomatic individuals suspected of having COVID-19 will need to be tested, and, if positive, quarantined and kept in the isolation room under close observation until they no longer test positive for the virus.

Treatment of COVID-19 may include: corticosteroids, recombinant fusion protein (ACE2-Fc), ACE2 blockers, human gamma globulin injections (human γ-Globulin) at a dose of 5g/day, IFN-α (interferon alpha),  cpap (positive airway pressure) therapy and antiviral drugs, such as oral ribavirin (tribavirin), Tamiflu® (Oseltamivir phosphate), or  Kaletra® (lopinavir/ritonavir), along with broad-spectrum antibiotics and supportive care.

The ACE2-Fc therapy: Novel ACE2-Fc fusion protein can be used as a therapy against 2019-nCoV coronavirus, as well as it can be used for diagnosis, and prophylaxis of 2019-nCoV. These fusion proteins neutralized 2019-nCoV and SARS-CoV in vitro

Fusion proteins (recombinant ACE2-Ig) has high affinity binding to the RBD (receptor-binding domain) of 2019-nCoV and SARS-CoV, this novel recombinant protein (ACE2-Fc) was generated by connecting the extracellular domain of human ACE2 to the tail region (the Fc region) of the human immunoglobulin IgG1 (human igg1 antibody)

The Fc region of an antibody interacts with cell surface receptors (Fc receptors)

Novel Inhibitors, like Enfuvirtide and SC29EK are used to block SARS-CoV-2 entry to host cell, these anti-ACE2 peptides or antibody work by blocking the surface ACE2 receptor

Experimental drugs, like Remdesivir showed promising results against COVID-19. Remdesivir works by inhibiting RNA-dependent RNA polymerase (RdRP, RDR) or RNA replicase of coronaviruses, an enzyme that catalyzes the replication of RNA from an RNA template

Findings of the first clinical trial of Remdesivir in COVID-19 patients is coming in a matter of weeks

Remdesivir, an antiviral drug in the class of nucleotide analogs, neutralized the viral pathogens of SARS and MERS in animal models in vitro and in vivo

Statins and angiotensin receptor blockers (ARBs) have been effective in treating COVID-19 patients

Angiotensin II receptor blockers (ARBs, ACE2 blockers), like Losartan (Cozaar), Azilsartan (Edarbi), Eprosartan, Irbesartan (Avapro), Olmesartan, Candesartan (Atacand) can be used to prevent the host response to emerging virus diseases, these drugs can also be used for controlling high blood pressure (ACE2 blockers dilate blood vessels), preventing kidney failure, and treating heart failure

Prevention – For High risk individuals

Usual adult dose of Losartan to prevent the host response to emerging viral diseases:

Initial dose: 100 mg orally once a day

Supportive dose: 0.7 mg per kg orally once a day (up to 50 mg total) for 30 days. The lowest price for losartan (Cozaar) 50 mg is $0.07 (up to $0.67) per pill

This drug is not suitable for children younger than 6 years and pregnant women, as it acts directly on the RAS (renin angiotensin system) and can cause injury and death to the developing fetus

Anti-viral immunotherapy

Interferon alpha (IFN-α) can be used to treat several viral infections such as hepatitis B and C. Interferons stimulate the virus-infected cells and those nearby to produce proteins that prevent the 2019-nCoV from producing and replicating its RNA within them, thus boosting their anti-viral defenses. IFN-α preparations, such as Infergen® (Interferon Alfacon-1), are injected intramuscularly or subcutaneously to inhibit SARS-CoV-2 replication

Low‐dose oral interferon alpha as prophylaxis against COVID-19

Treatment with IFN-γ (gamma-interferon) preparations, such as Actimmune®, is recommended to inhibit the replication of SARS-CoV-2

Combination therapy of Zidovudine (azidothymidine, ZDV, AZT), an antiretroviral medication, and IFN-α synchronously inhibit the growth of HIV/AIDS in vitro




  1. medcoi.science [Latent SARS-CoV-2 in the salivary glands]
  2. who.int/docs/default-source/coronaviruse/situation-reports/20200712-covid-19-sitrep-174.pdf
  3. who.int/csr/resources/publications/StandardPrectHC.pdf [who cough etiquette]

Verified by: Dr.Diab (October 7, 2022)

Citation: Dr.Diab. (October 7, 2022). What is COVID-19 pandemic? Symptoms Diagnosis and Precautions. Medcoi Journal of Medicine, 34(2). urn:medcoi:article20950.

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