Coronavirus by age group | COVID-19 splitting generations

Coronavirus by age group | COVID-19 splitting generations

March 26, 2020 0 By Santiago
Reading Time: 10 minutes

So much information about who’s affected by the coronavirus and COVID-19 that you ultimately feel like you know even less. Let’s divide the situation with the new coronavirus by age group and explain why we see symptomatic differences, and why everybody needs to participate in the recommended safety measures.

The new coronavirus took the world with a storm. Months have passed, and people are still wondering “what’s going on?” I’m locked in as part of a nationwide quarantine and, while it might not be how I imagined my spring, I’m all in (literally). Fortunately, it feels like most in my surroundings seem aware of the delicate situation. But, the overwhelming information from the media, neighbors, and coworkers has left you with more knowledge gaps and questions. The more you know, the less you know.

Kind of related: we published a post a couple of weeks back that looked into the misconceptions linked with the basic reproduction number (or R0) of the new coronavirus SARS-CoV-2. Have a look at the post here to learn how it’s estimated.

Still, a lot of questions remain. For example:

  • Who’s in the high-risk group?
  • Why do so many old people get sick and die?
  • Do children get symptoms, or even infected by the new coronavirus?
  • Why do young people need to protect themselves? It’s just flu-like symptoms, right?  

Do you know why these things matter?

Let’s go from old to youngest to analyze the differences related to the new coronavirus by age groups and understand the situation a bit better. Let’s start with old ones.

By the way, to be clear: the new coronavirus is named SARS-CoV-2 and the disease it causes is COVID-19. I’ll refer to SARS-CoV-2 as the coronavirus or the new coronavirus in most of the text.

The oldies in the high-risk group

At first, YouTube videos showing random people in China falling on the streets got viral. Eventually, however, we started to see a pattern: old people (70+) were in the high-risk group. They risk severe symptoms and have the highest proportion of death. Italy, with one of the oldest populations in the world, woke us up when we thought the thing was confined to China. But why the old generations? 

Why old adults are at higher risks of COVID-19

We can explain the trend in two parts that are closely related: a weakened immune system and a higher prevalence of chronic diseases.

A weakened and less specific immune system

As people get older, the immune system starts dropping, a phenomenon called immune system aging. The process includes a reduced production of immune cells (white blood cells) in the bone marrow and can start after you turn 70. The reasons for this decline can be many, but changes to the stem cells that produce the immune cells are important factors. The aging immune system fails to protect these age groups from infectious diseases and cancer.

Diagrams representing the fatality rate caused by COVID-19 in China. Credits: Wikipedia Commons. Published under creative commons CC-BY-SA-4.0,

One thing is worth noticing here. Since your genes usually don’t change much during your lifetime, non-genetic changes are often the cause of a weakened immune system. In a quite recent post, we described the role of epigenetics in health and disease. In short, epigenetics is the permanent or temporary control of gene expression without changing the genetic code (you can read more about it here). So what causes changes in epigenetics then? Stress, food, sun exposure, exercise, love, sleep, toxins, drugs, (and rock’n’roll). Your environment.

Of course, a lowered immune system doesn’t explain the whole disease process in older adults. After all, the causes of death by COVID-19 are often related to an overresponsive immune system. And I don’t want to confuse you with mixed messages; I remember that I stated that a “declined immune system” was the bad guy earlier. But hear me out, our immune system carries out a diverse set of processes to protect the body from harm.

Simply speaking, we have two types of immune cells: the adaptive immune system and the innate immune system.

Think of the adaptive part as highly specialized immune cells that know which harmful or harmed cells to kill because they use their brains, they have immunological memory. This is the smart missile-like immune system that older people might have less of.

The innate immune cells, on the other hand, oh these suckers are goons with a search and destroy attitude. If they see foreign cells in the body, they start blasting. Once the smart adaptive immune system declines in old people, they begin to rely on these loose cannons. Don’t take me wrong, these killers are heroes in many ways; they save lives. But when you merely rely on the innate immune system, you get war.

And then we have the famous cytokine storm

Talking about war, the response many older people experience upon SARS-CoV-2 infection is called a cytokine storm. An uncontrolled storm of proteins called cytokines, whose task is to keep the immune system alert. This response can be devastating when overreacting, causing high fever, inflammation, and organ failure. The proinflammatory response that cytokine storms trigger may escalate the severity of the symptoms.

Unfortunately, common anti-inflammatory drugs have not shown promising results as treatments for cytokine storm. Although we have a good understanding of what causes an overreactive immune response, the clinics have limited treatment alternatives. But, recently, the US Food and Drug Administration (FDA) approved an arthritis drug called Actemra. Apparently, the treatment had successful outcomes in China.

In brief, the drug inhibits a specific cytokine called interleukin-6 (IL-6) from binding and activating its receptor. The IL-6 cytokine is upregulated and highly expressed in many disorders, including conditions related to the immune response. So, stopping this little protein can help repress its damaging actions.

To summarize, the on/off buttons of the immune system can cause devastating effects depending on the balance between different types of responses. Turning off the adaptive (brainy) cells and boosting the innate (goon) cells leads to trouble. And that, ladies and gentlemen, is one of the reasons why old people are so susceptible to SARS-CoV-2 and the resulting COVID-19 disease.

A higher prevalence of chronic diseases

The longer we live, the more we accumulate exposure to different types of stresses, such as external (for example, smoke, sun, or toxins) or internal ( for example, metabolism). Sure, humans (and other organisms) have developed amazing strategies to either prevent or repair damages to the DNA, cells, or tissues. Still, it can only do so much, and the older we get, the more likely it is that we accumulate issues that, ultimately, may lead to chronic conditions.

Many factors are involved in these processes, for example, lifestyle, environment, and genetics. The point is that older people have a heightened risk of underlying health conditions that are linked to severe COVID-19 related symptoms. According to the World Health Organization, these conditions include high blood pressure, heart disease, lung disease, cancer, or diabetes.

Coronavirus by age group mortality rate based on underlying dieseases
Representation of the mortality rate in China based on the most common underlying health condition. Credits:

In other words, the increased risk among older people is not only caused by a higher number of candles on their birthday cakes. It’s because many older adults have developed one or several high-risk conditions over the years.  

Related to this: How do we diagnose virus infections?

While grouping people into age categories to understand COVID-19 outcomes can be helpful (and I think it is), it may also be misguiding. Primarily since it masks the risks associated with the next age group on the list…

Why should youngsters be cautious or aware?

Now, let’s turn our attention for a brief moment to the young guns out there. And, I’m not only talking about Nickelback-loving, selfie-obsessed, 20-something-year-old kids (we still got luv for you). Although it feels like the cutoffs and age labels often change in the media and are sometimes arbitrary, I’ll include all you between 19 and 70. [I can hear all 60+ raising their arms to the new label.]

Youngsters, you’ve realized by now that you’re not in the risk zone and many of you have started wondering why the coronavirus related safety measures apply to YOU. “Why can’t I go outside? I mean, it’s only a fever, it’s not like I’m going to die.”

Let me clarify that younger people are far from immune or asymptomatic. We’ve seen, for example, that about 25 percent of hospitalizations in Italy (one of the most affected countries) are below 50 years old. And even though the death percentage in this age group is less than 1 percent, underlying health conditions do affect the outcome of the infection. So yeah, you’ll PROBABLY have milder symptoms.

Nevertheless, the main reason we’re participating in safety measures is to protect the older and sick people from life-threatening diseases and symptoms (see above). And although you don’t have symptoms, stay at home or at a distance from people for a while. You could be a so-called invisible carrier, meaning that you may carry the virus without experiencing any symptoms.

By taking protective measures like staying at home, washing hands, and keeping proper distance, the young, healthy part of the population help reducing the virus spread.

The mild symptoms that may spread the disease

Actually, don’t celebrate that you and your other healthy Candy Crush-playing youngsters only get mild or undetected symptoms. The fact that young people’s symptoms often go undetected, resembling regular flu or a common cold, might be the root cause of its impressive spread around the world.

My neighbor recently asked me if I’d ever experienced a similar situation like the one we’re experiencing with the coronavirus. He asked me why we didn’t undergo this with Ebola or SARS; sure, people were freaking out but no pandemic. The reason may be that both Ebola and SARS have short incubation times (early symptom-onset upon infection), and that infected individuals are most contagious once they have symptoms.

That’s not the case with the coronavirus SARS-VoV-2, which can linger in your cells and spread to other people while you’re asymptomatic (estimated incubation period of between 1 and 14 days). So you might have the virus without knowing and still be infect other people (for example old ones). On top of that, today’s competitive society almost encourages people not to stay at home because of a simple common cold; or even fever. It drives me insane, but that’s what people do.

What’s the deal with the kids and coronavirus and COVID-19?

Do kids get infected by this coronavirus? Do they get symptoms? Are they invisible carriers?

Like always, kids are an enigma. Why do they behave the way they do? And now, on top of their childish behavior, they seem unaffected by the coronavirus. What the eff is up with that?

Well, that’s not entirely true. Although we’ve been through waves of headlines claiming that children cannot get infected by the virus (a message that ultimately toned down) we now know that children under 19 years of age experience symptoms. China, for instance, reported 2.4 percent of cases in this age group, and 2.5 of these cases (which means 0.06 percent of the total) experienced severe symptoms.

So, children seem to be getting sick from the coronavirus, and they even seem to get COVID-19 symptoms. Most of them experience mild to moderate symptoms. Still, some of them (usually the toddlers younger than 1 year in the case above) experience severe symptoms.

Why do children show different COVID-19 trends?

An interesting question is why the children’s condition has been so obscure and hard to confirm. Different theories present valid reasons (and I’ll be speculating at times here).

One reason might be that children continually excrete that green slime from their noses; they always seem to be sick somehow. Parents might not react to what seems like yet another episode of flu or a common cold, and they choose to let nature and time take their courses. In other words, they don’t get hospitalized, which, in turn, means that they don’t get diagnosed. How many might have COVID-19 without the parents even noticing?

Another reason is that children usually don’t have any underlying health conditions, as we discussed above. For example, very few kids have diabetes, heart conditions, or are obese. Remember, these conditions predict symptom severity in COVID-19.

The last reason might be a bit confusing but keep in mind that we, at this stage, don’t know why children react differently to this coronavirus (SARS-Cov-2). I explicitly showcased the name of the virus here because the last reason is that children might experience milder symptoms due to earlier exposure to other coronaviruses. You know, in the playground. That’s right; if you get exposed to a virus, you start creating antibodies against that specific pathogen. SARS-CoV-2 is not the only coronavirus out there (it’s one of seven) and children may be exposed to the other forms. The other coronaviruses kind of match the profile of the current one (SARS-Cov-2). In this scenario, the kids have their immune system prepared. “Argh! Let them come! There is one dwarf yet in Moria who still draws breath!” (for you nerds)

And then the confusing part. Maybe, because children haven’t lived as long as us adults, they never developed the “wrong” antibodies against other coronaviruses. It’s the opposite argument, but still valid. We can imagine that adults have encountered many other coronaviruses during their lifetimes and developed antibodies against these. These work fine as long as they perfectly match the virus. But they might not completely recognize SARS-CoV-2 (only partly), which may elicit a condition called antibody-dependent enhancement that can benefit a virus. The phenomenon may even help the virus to enter your immune cells (white blood cells) and spread.

Again, these are theories, and we don’t seem to really know why children present another clinical picture.

Did splitting the coronavirus by age groups help?

Three generations. Private PictureFritz Packenius (Photographer from Bielefeld) / CC BY-SA

In my opinion, both yes and no. On the one hand, it simplified our understanding of the disease trend and categorized it for us. Old people can get sick and die, which is bad. Young people have a lower risk but also a responsibility, which is good. Children don’t get too sick, which is confusing.

On the other hand, the simple categorization by age groups left many people out of the discussion, for example, the obese, diabetic younger individuals with heart problems. Many supermarkets have specially dedicated opening hours for the elderly – and that’s great – but the signs do not welcome the obese diabetic. How do we include these in the safety zone?

I’m happy to see people taking care of each other in these times of insecurity. We don’t even know for sure which strategy works the best to diminish the spread, but godammit, we follow recommendations because we care for each other.

Locked up in my apartment (with enough toilet paper rolls) I’m thinking, “What’s up with the TP hysteria?”

Anyway, the next post might deal with an unrelated topic, such as babes in research or cancer-sniffing dogs. But, considering the situation, we might do another coronavirus post. Until next time, stay safe.

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