healthHealth and Medicine

This Is What COVID-19 Does To The Human Body


Madison Dapcevich


Madison Dapcevich

Freelance Writer and Fact-Checker

Madison is a freelance science reporter and full-time fact-checker based in the wild Rocky Mountains of western Montana.

Freelance Writer and Fact-Checker


Novel Coronavirus 2019 disease, COVID-19, has SARS-like respiratory symptoms. Joel Bubble Ben/Shutterstock

With more than 116,000 cases of the new coronavirus globally and over 4,000 deaths (at the time of writing), experts are sounding the alarm on the potential for widespread community transmission at the local level. IFLScience spoke with health experts to understand the potential for the virus to reach pandemic proportions through its unique ability to attack the human body.

Experts with the Centers for Disease Control and Prevention say that Americans should prepare for a “significant disruption of their lives” from disease transmission. At least 26 people in the US have died as a result of COVID-19, with a total of 423 cases reported from coast to coast.


How Does COVID-19 Attack The Human Body?

Much is left to be discovered about how COVID-19, the respiratory illness caused by the virus SARS-CoV-2, attacks the human body. Last month, the Chinese Center for Disease Control and Prevention published clinical details on the first 72,000 patients diagnosed through February 11, 2020.

COVID-19 is “similar to but distinct from” severe acute respiratory syndrome (SARS), allowing scientists to use what is known about SARS to inform knowledge about novel coronavirus. Just like the flu, COVID-19 begins in the lungs and spreads via water droplets when a person sneezes or coughs. (COVID-19 may also spread through poop but further research is still needed.) The WHO reported that SARS attacked the body in three phases: viral replication, immune hyperactivity, and pulmonary destruction, which appears to be similar to how COVID-19 attacks.

Early studies suggest COVID-19 replicates efficiently in the upper respiratory tract. Infected people produce a large quantity of the virus at the beginning of the infection and new research revealed the incubation period of the infection is 5.1 days, where those infected do not exhibit any symptoms, which allows them to carry on as normal and contribute to the spread of the virus. COVID-19 presents in three patterns of infection: It begins with mild illness and upper respiratory tract symptoms, followed by non-life-threatening pneumonia. After about a week, severe pneumonia with acute respiratory distress syndrome can progress rapidly and sometimes require life support.


When infected, the body triggers a cytokine response whereby immune cells attack the virus. In some cases and for reasons unknown, the virus may trigger an overreactive response from the immune system, which can further dampen recovery efforts.

Travelers in Sichuan, China, wear masks to prevent the spread and transmission of novel coronavirus 2019. B.Zhou/Shutterstock

What are the symptoms?

IFLScience spoke with WHO spokesperson Carla Drysdale who said that 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 that are usually mild and begin gradually. Some people who are infected do not develop any symptoms and don’t feel unwell, while around 80 percent of people recover from the disease without needing special treatment.

“Around 1 out of every 6 people who get COVID-19 becomes seriously ill and develop difficulty breathing. Older people, and those with underlying medical problems like high blood pressure, heart problems, or diabetes, are more likely to develop serious illness,” said Drysdale, adding that about 2 percent of people with the disease have died.


Clinical management guidelines currently recommend a patient be discharged from the hospital after two consecutive negative results at least 24 hours apart. Currently, there is a period of about 20 days between the onset of symptoms and full recovery, but Drysdale notes that COVID-19 is a new disease and experts need more epidemiological data to determine whether a person is immune following infection.

It is also inaccurate to compare COVID-19 to the annual influenza virus as Drysdale said it is a “unique virus with unique characteristics.” Both COVID-19 and influenza cause respiratory disease and spread the same way (via small droplets of fluid from the nose and mouth of someone who is sick), but there are important differences between the two.

“First, COVID-19 does not transmit as efficiently as influenza, from the data we have so far. With influenza, people who are infected but not yet sick are major drivers of transmission, which does not appear to be the case for COVID-19,” she added. “Evidence from China is that only 1 percent of reported cases do not have symptoms, and most of those cases develop symptoms within 2 days.”

Furthermore, there is currently no vaccine to prevent COVID-19 – though there are about 20 in development globally and 80 clinical trials set to launch – and there is little immunity in the world population given the novelty of the virus.


Expert Warns That COVID-19 Is “Already A Pandemic”

Much of what experts have seen in terms of attack rates have been published by the Chinese Center for Disease Control and Prevention. A recent paper shows that there are varying levels of attack rates by age, mostly lower rates in children, which Drysdale said is “important and warrants further study,” but it is still quite early to know for sure. Higher contraction rates are seen in adults, with transmission being driven by close contacts between families.

The WHO has declared COVID-19 a “public health emergency of international concern” – the organization’s highest level of alarm – but contends that it “no longer uses the system of six pandemic influenza phases.” IFLScience spoke with Gregg Gonsalves, an epidemiologist at the Yale School of Public Health, who said that the spread of coronavirus 19 is a pandemic even if the World Health Organization hasn’t yet declared it as such.

“It has spread to over 50 countries and there is community spread in the US,” he added. “It is a pandemic already – the difference is the scale and scope. A lot of that is do we react to it or do we act out of fear and ignorance.”

Testing kits created by the CDC. Wikipedia Commons 

Over 450 public health and legal experts signed a public letter to the US government declaring that widespread transmission of COVID-19 within the country is “inevitable” and a successful response is needed to ensure the health and safety of the general public. Gonsalves said that leaders should first shift resources toward healthcare facilities so that medical professionals are fully equipped to handle surges in patient care. Communities also need to prepare for telecommuting options wherever possible and to put measures into place to support sick leave for workers who do not have paid-time-off, as well as lift immigration enforcement so that everyone may receive healthcare, such as during September 11 and Hurricane Katrina.

“We need to put the immigration debate on hold while we’re dealing with this public health crisis,” said Gonsalves. “If someone is sick and they’re afraid to go to the hospital, it’s not just endangering their lives but it’s also making it harder for everyone else to stay safe.”

“We need to make sure the messaging about this is based on evidence and not fear and paranoia. It is important to let scientists lead the discussion and put them out front, as well as to make sure any misinformation is quickly corrected,” said Gonsalves.

Experts say the best protection against COVID-19 are non-pharmaceutical interventions, preventative steps such as washing hands thoroughly, covering coughs and sneezes with a tissue, disinfecting surfaces around the home and workspace, and avoiding contact with people who are known to be sick. People with fever, cough, and difficulty breathing should seek medical attention and stay home unless told otherwise.

This scanning electron microscope image shows SARS-CoV-2 in yellow. NIAID Rocky Mountain Laboratories (RML), U.S. NIH/Wikimedia Commons


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