This Is Why Some People Have Coronavirus Symptoms and Others Don't

Depending on the host, COVID-19 presents itself differently. Here's why some people are asymptomatic.

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As you surely know by now, the coronavirus doesn't look the same in everyone it infects. Some people have respiratory symptoms, others have gastrointestinal symptoms, some can't smell or taste, and others have no symptoms at all. There are many mysteries brought forth by the COVID-19 contagion, but none may be greater than why it's killing some people and barely affecting others. Internist Natasha Fuksina, MD, of astraMDhealth in New Jersey, has some insight as to why certain people with coronavirus are asymptomatic.

Fuksina says that the current assumption is that 25 percent of the infected COVID-19 population "remains asymptomatic and never develop symptoms or have positive findings on chest X-rays." However, some studies have shown that as many as 80 percent of those with COVID-19 are "silent carriers," showing no or very mild symptoms. Why that is is a big question plaguing the medical and scientific communities.

While it'd be easy to assume that asymptomatic carriers of COVID-19 are healthier than those who come down with bad—or even deadly–cases, it's not as simple as that, Fuksina explains. "While intuitively one might think that a person who is truly asymptomatic … is a healthier one, there are many factors here at play," she says.

Firstly, there's the imperfect testing symptom for COVID-19, which is a significant issue. There's anywhere from a 3 to 15 percent rate of false positives and false negatives, which may label someone as a carrier who actually isn't or count someone as negative when they do have the coronavirus.

Also, Fuksina says, the amount of viral load matters, meaning how much someone is exposed to the COVID-19 contagion. "Some health care workers on the frontlines get very sick when they are exposed to large amounts of viral particles," Fuksina explains. "If a person has inhaled a small amount of viral droplets and their immune system was able to launch a successful attack on the virus, they may have never gone on to develop any symptoms."

As for why COVID-19 presents with symptoms in some but not others, Fuksina says, "I am inclined to extrapolate from the known facts that older and sicker patients with weaker immune systems develop more severe illness. People with stronger immune systems will also have a tendency to produce a quicker and adequate response to kill the virus before it starts replicating and producing overt symptoms."

To put it simply, older individuals who are either already sick or have compromised immune systems are likely to have symptoms, while those with stronger immune symptoms are able to handle the virus much better. Basically, "a person needs to be generally healthy to be able to mount an appropriate immune response to the infection," Abela Mahimbo, PhD, a public health expert, wrote in The Conversation.

"We will need to design a study where we test large population samples … to be able to back up this assumption scientifically," Fukisina said. "As testing is becoming more widespread, we will be able to learn immune and metabolic characteristics of those who remain truly asymptomatic carriers." And for more facts to know about COVID-19, check out 21 Coronavirus Myths You Need to Stop Believing, According to Doctors.

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