Supervisor Elham AbolFateh
Editor in Chief Mohamed Wadie

Do You Know COVID-19 Has Various Levels of Severity? Op-ed


Tue 28 Apr 2020 | 11:37 PM
Hassan El-Khawaga

Coronavirus disease (COVID-19) is caused by SARS-COV2 and represents the causative agent of a potentially fatal disease that is of great global public health concern.

To explain the different processes that occur within the body, we have split the disease into four separate phases that roughly match the different levels of severity: mild, moderate, severe, and critical, Dr. Magdy Badran says.

In reality, the physiological processes underlying these phases overlap. People with COVID-19 may or may not show features of earlier or later phases.

Phase 1: Viral Replication in The Nose

Both SARS-CoV-2 (COVID-19) and SARS coronavirus (SARS-CoV) gain entry via a receptor called ACE2. The infection begins when the long spike proteins that protrude from the virus particle latch on to the cell’s ACE2 protein.

ACE2, More commonly known for its role in controlling blood pressure and electrolytes, these receptors are also present in the nose, lungs, back of the throat, gut, heart muscle, and kidneys.

Recently, scientists have found ACE2 receptors in the mouth and tongue, potentially indicating a hand-to-mouth route of transmission. Once inside the cell, the virus’s genetic material directs the cell to manufacture millions of new copies of itself.

Viral replication in the nose is important for the early spread of the virus. On average, swabbing the upper respiratory tract during the first 5 days of symptoms show about 676,000 copies of the virus per swab.

Phase 2: Viral Replication in The Lung

Viral load is simply the amount of virus in the body. This varies in different parts of the body and can change over time. The viral load in the lungs of COVID-19 patients is greater than that in the nose.

A patient’s viral load increases as the virus replicate and disease symptoms get worse and then decrease as the patient recovers.

The “incubation period” is the time between catching the virus and beginning to have symptoms of the disease. Most estimates of the incubation period for COVID-19 range from 1-14 days, most commonly around five days.

In contrast to the falling numbers of viral units in the upper respiratory tract, numbers in sputum rose for most of the patients. The virus in the sputum may be present for 4 weeks, with an average of 7 million units in 1 milliliter. This amount is about 1,000 times more than that in people with SARS.

The most common symptoms of COVID-19 are fever, tiredness, and dry cough. Some patients may have aches and pains, nasal congestion, runny nose, sore throat, or diarrhea.

These symptoms are usually mild and begin gradually. Some people become infected but don’t develop any symptoms and don't feel unwell.

Most people (about 86%) recover from the disease without needing special treatment. They will have a mild or asymptomatic disease, with common symptoms including fever, cough, and loss of sense of smell.

Phase 3: Pneumonia

Approximately 14% of people with COVID-19 will have severe disease and may need to be treated with oxygen in a hospital. Of these inpiduals, 75% will have evidence of bilateral pneumonia.

About 5% of people have critical infections and need a ventilator.

Anyone can get COVID-19 pneumonia, but it’s more likely in people who are 65 or older. Those who are 85 or older are at the highest risk.

People who live in nursing homes or who have other health problems also have higher chances of more severe illness with COVID-19. The list includes moderate to severe asthma, lung disease, high blood pressure, heart disease, diabetes, liver disease, renal failure, and severe obesity.

Someone who has a weakened immune system may be more likely to get severe COVID-19 illness, too. This includes smokers, people being treated for cancer, people who have had a bone marrow transplant, people who have HIV or AIDS that’s not under control, and anyone who takes medications that slow the immune system, like steroids.

Pneumonia in COVID-19 occurs when the lung consolidates and collapse. The reduced surfactant in the alveoli from the viral destruction of pneumocytes makes it difficult for the lungs to keep the alveoli open.

As part of the immune response, white blood cells rush into the alveoli. Meanwhile, blood vessels around the air sacs become leaky in response to inflammatory chemicals that the white blood cells release.

This fluid puts pressure on the alveoli from outside and, in combination with the lack of surfactant, causes them to collapse.

As a result, breathing becomes difficult, and the surface area in the lung where oxygen transfer usually takes place becomes reduced. The patient may show rapid heartbeat, shortness of breath or breathlessness, rapid breathing, dizziness, and heavy sweating.

Most patients will recover at this stage with supportive intravenous fluids and oxygen via a mask or an external positive pressure mask.

Phase 4: The Cytokine Storm

The most common time for the onset of the critical disease is 10 days, and it can come on suddenly in a small proportion of people with mild or moderate disease.

People who get pneumonia may also have a condition called acute respiratory distress syndrome (ARDS). It’s a disease that comes on quickly and causes breathing problems.

Cytokines are chemical mediators that white blood cells such as macrophages release, and they can engulf infected cells. These cytokines — which have names such as IL1, IL6, and TNFα — have actions that include dilating the vessel walls and making them more permeable.

In extreme circumstances, this can lead to a collapse of the cardiovascular system and multiple organ failure.

In ARDS, the inflammation stage gives way to the fibrosis stage. Fibrin clots form in the alveoli, and small blood clots pepper the small blood vessels in the lung that are responsible for gas exchange with the alveoli.

Estrogen in mouse cells suppresses the release of cytokines from macrophages, this could be one explanation for worse outcomes from COVID-19 in males.

More research is necessary to understand the physiology of this challenging new disease.

Prevention Tips

People should wash their hands regularly with soap and water, or clean them with an alcohol-based solution. Disinfect surfaces like kitchens and work desks regularly.

Seek information on the situation from reliable sources, like a local or national public health agency, WHO, or local health care professional. Cough or sneeze into a sleeve or tissue. Throw the tissue away and wash hands.

People over the age of 60, or anyone with an underlying health condition, have a higher risk of contracting a severe case of the disease.

Those people might need to take extra precautions to avoid crowded places and sick people. If a sick person does stay at home, he should eat and sleep separately from anyone else in the household. He should also use different utensils to eat. A person should seek care immediately if he develops shortness of breath.