Viruses 101: Why the new coronavirus is so contagious and how we can fight it

Learn why the new coronavirus is so contagious. Is a cure or vaccine for COVID-19 coming? And will summer make a difference?
March 17, 2020
a photo of blood with coronvirus on the label
Why is the coronavirus so contagious? Learn how viruses get into our cells and how medical experts are fighting back. Photo: Getty Images.

Experts in infectious diseases don’t want people to panic over the new coronavirus, but they do encourage everyone to take this pandemic very seriously and to do all we can to prevent the spread of the virus.

As the number of cases spikes in Colorado and throughout the U.S., we consulted medical experts on how viruses behave, why the new coronavirus is so contagious and whether the virus could dissipate as we move from spring into summer.

Dr. Kenneth Tyler is Chair of the Department of Neurology at the University of Colorado School of Medicine and the department’s Louise Baum Endowed Professor. He sees patients and supervises medical students at UCHealth University of Colorado Hospital and at the Veterans Affairs Medical Center in Aurora. He’s a professor of immunology and microbiology with sub-specialties in virology and infectious diseases.

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Many viruses cause neurological symptoms in patients and Tyler specializes in infections in the central nervous system. He has treated patients extensively for viral diseases including West Nile, herpesviruses, enteroviruses and others.

One of the physicians on Tyler’s team is Dr. Daniel Pastula. He has worked on the front lines of epidemics around the world, including outbreaks of illnesses like West Nile and Zika and a rare polio-like illness called Acute Flaccid Myelits.

Pastula has assisted local public health officials in Summit County in recent days as they have tried to fight the growing epidemic. He is now back home and minimizing social contact as he follows current guidelines from the Colorado Department of Public Health and Environment (CDPHE).

Pastula is a neurohospitalist at UCHealth University of Colorado Hospital and an associate professor of neurology, infectious diseases and epidemiology for the University of Colorado School of Medicine and the Colorado School of Public Health.

He did part of his training in epidemiology and infectious diseases with the Centers for Disease Control and Prevention.

Why is the new coronavirus so contagious and spreading so quickly? Is there something about it that makes it a super villain among viruses? Or is it just behaving the way viruses do?

What makes the new coronavirus so dangerous to humans is simply that it’s “novel,” meaning it’s new to humans, so we don’t have any way to fight it.

“This is the first time it’s ever circulated in humans,” Pastula said.

Dr. Dan Pastula
Dr. Dan Pastula

So, the virus isn’t more powerful, per se, than other viruses. But when it enters the human body, we have no pre-existing defenses since our bodies don’t immediately recognize it as a dangerous intruder. Imagine an old, walled medieval town. If this virus were a disguised attacker arriving at the town’s protective walls, but open gates, the guards would not immediately know to be suspicious. With this coronavirus, it’s as if the guardians of our cells have kept the gates open and let the coronavirus in without immediately recognizing its danger.

Then the virus starts to spread.

“It gets in and hijacks the human cell’s machinery. Instead of the cell doing what it’s supposed to do, the virus overrides the cell’s normal programming and turns it into a machine to make more of the virus. It goes and goes and goes until the immune system stops it,” Pastula said.

“The virus is simply a blueprint or a code to turn cells into machines to make more virus,” he said.

For a great visual explanation for how this coronavirus attacks cells, view these illustrations from the New York Times.

Is there a cure for this new coronavirus?

No. Since this is an entirely new kind of coronavirus that humans have never seen, there is no cure. Experts are now testing both anti-viral medications and vaccines, but it’s unlikely that we will have a vaccine to prevent COVID-19 for at least a year.

“We need to make sure any vaccines are both safe and effective,” Pastula said. “To do all those checks will take at least a year.”

While there’s no cure for COVID-19 now, the prospect a vaccine down the road offers great hope for the future.

“Vaccines have been a tremendous asset in eliminating many once-deadly viral infections,” Tyler said. “The poster child for this is small pox, which was totally eradicated through vaccine campaigns.

“Polio is almost gone as well,” Tyler said.

Dr. Ken Tyler
Dr. Ken Tyler

Another extremely contagious illness that vaccines can prevent is measles. Unfortunately, if people fail to get their children vaccinated the overall level of “herd immunity” drops and the virus can surge again — as we have seen in the U.S. recently.

Prevention, rather than treatment once symptomatic illness occurs, is the best way to reduce the harm from viruses.

“There is hope that we can develop a vaccine for this new coronavirus,” Tyler said. “I don’t see any expert who says it will take less than a year. That’s not for this epidemic now. But, if this coronavirus recurs in the future, a vaccine might be helpful then.”

The first human trials of potential coronavirus vaccines have just started in Seattle.  These typically are designed to see if a potential vaccine is safe and if it induces a robust immune response.

The other great hope is anti-viral medications. There is still no vaccine to prevent HIV, the virus that causes AIDS.

But, Tyler says, people with HIV and AIDS do very well now thanks to an array of medications.

“We have wonderful anti-viral drugs that have totally changed what the disease is,” Tyler said.

Since there are no known treatments for COVID-19, doctors are experimenting with existing anti-viral medications now used for the flu and AIDS.

“That is something that could happen on a much quicker time frame (than a vaccine) especially if researchers identify existing drugs for other purposes. That’s exactly what’s going on now,” Tyler said.

Sometimes drugs that are already proven to be safe and effective for one disease can have surprising therapeutic benefits for a new illness, like COVID-19, Tyler said.

“There are thousands of approved drugs. Sometimes interesting things pop out that you never would have thought of.  We had a sneak peak at this type of coronavirus with SARS and MERS,” Tyler said.

So, it’s possible a drug could emerge quickly.

“Is something ready for prime time with proven efficacy against COVID-19 today? No. Are there medications that doctors are giving to people? Yes,” Tyler said.

Will this virus dissipate in the spring, like the seasonal flu typically does?

Unfortunately, it’s not clear whether the new coronavirus will stop spreading as the weather warms this spring.

“The bottom line is that we don’t know if this virus is going to show a seasonal disappearance,” Tyler said. “There’s some indication that some of the related coronaviruses — SARS and MERS — did seem to show a seasonal pattern and some evidence has emerged from China that Covid19 cases may be waning, but we don’t know what will happen here or when.”

There have been cases of COVID-19 in South America and Australia, where the season is shifting from summer to fall. So far, the numbers of sick people in the southern hemisphere have trailed the number of people who have become sick in China, other parts of Asia, Europe and the U.S. But, it’s unclear why the virus is moving around the world as it is. Only time will tell exactly how the weather and warming temperatures will influence the behavior of this new coronavirus. (Click here to see data from Johns Hopkins about COVID-19 cases around the world.)

Furthermore, different viruses behave differently. Influenza or the seasonal flu typically does the greatest harm during the winter months. Experts believe that’s because more people are indoors during colder months and in close contact with one another. But other viruses behave differently.

Another type of virus called an enterovirus is causing a new, rare polio-like illness that is sickening children and young people and causing some instances of paralysis.  It’s called Acute Flaccid Myelitis or AFM. The virus that causes AFM circulates in August and September and has shown a confounding pattern of returning every other year.

And, decades ago, the virus that caused polio struck people more during summers. Older adults alive today still remember summers as children when swimming pools and lakes were closed due to fears about the spread of polio.

“A lot of viruses that we are exposed to, but not all of them, do seem to show these seasonal predilections,” Tyler said. “Sometimes it’s easy to understand why. Since West Nile is transmitted by mosquitoes, the virus is worse in the warm weather and infections drop when the cold weather emerges in the fall.”

But since COVID-19 is spreading from human to human, it’s not clear what will happen.

“There isn’t some magic that says exactly what the pattern will be,” Tyler said.

Are humans dealing with more viruses than in the past?

Viruses have always existed and they continually evolve and change, Tyler said.

“They’ve always been common. As far as you go could back in human recorded history, you could have found viruses and viral infections,” Tyler said.

But some of the viruses that have caused great harm to humans in recent decades —including this new coronavirus and its predecessors, SARS and MERS — have jumped from animals to humans. That was also true for the virus that causes AIDS.

“These viruses frequently had niches in animals,” Tyler said. “As human behavior changes, whether it’s our dietary habits or growth of cities that push us into contact with things we weren’t previously in contact with, we get exposed to new viruses.”

What’s the difference between a viral infection and a bacterial infection? Why don’t we have any medications to fight this new coronavirus?

Bacteria are living organisms. Antibiotics work to fight bacterial infections. And, there are broad-spectrum antibiotics that can fight numerous different types of bacteria. They serve as a “magic bullet” of sorts, Tyler said.

Unfortunately, anti-viral medications don’t work that way. Each virus is different. And anti-viral medications work by targeting specific viruses.

“We have drugs that help with AIDS, but they don’t help with herpes,” Tyler said.

That’s one of the reasons we have to get annual flu shots. The strain of the influenza virus that strikes each winter changes from year to year. So, each year, flu experts have to create a new vaccine based on the type of flu they predict will circulate that year.

Antibiotics don’t work against viral illnesses like COVID-19.

Medical experts are racing now to develop vaccines for COVID-19. And, around the U.S. and the world medical providers are experimenting with anti-viral medications to see if any will help patients who have the new coronavirus.

How does this virus spread?

“In terms of transmission, this virus appears very similar to other coronavirus strains. It travels through infectious droplets. If someone coughs or sneezes, the droplets fall to the surface. If someone touches that surfaces, then touches their face, they can get the new coronavirus,” Pastula said.

Virtual urgent care is available for people in Colorado.
Source: Getty Images

It’s also possible to have someone sneeze or cough directly towards you, though infectious droplets can only really travel a maximum of about 6 feet before falling to the ground, Pastula said.

That’s why public health experts are urging people to keep their distance from one another.

I hear the common cold is a type of coronavirus. Why can I get colds over and over?

“The common cold isn’t caused by a single virus. There are many viruses that cause the common cold. So you can get a cold multiple times because there are different viruses,” Pastula said.

In addition, immunities to various viruses wane over time. If you’ve had a particular type of virus once, you will have partial protection if you get it again.

“But, in terms of how much and for how long, we don’t fully know,” Pastula said.

Is climate change exposing humans to more viruses?

“Climate change can influence certain types of viral infections like West Nile,” Tyler said. “Some viruses are transmitted to people through vectors like mosquitoes or ticks.”

When climate change causes longer seasons with higher temperatures or greater rainfall, mosquitoes can thrive and infection rates from viruses they carry can climb.

Colorado has moved into what infectious disease experts call the “community transmission” phase of this epidemic. What does that mean?

In the initial fight against coronavirus, public health experts tried to keep the virus out of the U.S. When the first cases surfaced here, public health officials worked hard to do what they call “contact tracing.” They worked to find each person who had had contact with the person who had a confirmed case of COVID-19. Then, those people were placed in isolation. But now, the virus is spreading from human to human widely throughout the community. That’s why government leaders are now taking dramatic steps to close public venues and are encouraging people to reduce their contact with others so they can slow the spread of the new coronavirus. We have now moved from containment of the epidemic to mitigation, meaning reducing the number of people who get infected at the same time.

hand washing helps prevent coronavirus or flu
Source: Getty Images.

How can I avoid getting this coronavirus?

The advice sounds simple and you’ve heard it over and over again. But, the experts all agree.

“It’s very important to wash your hands frequently (soap and water works best) and not to touch your face with unwashed hands. Contaminated hands are the No. 1 way that this virus is transmitted. You can get it from touching a surface that has virus on it, then touching your face,” Pastula said.

How can I protect my family?

young girl coughing into her arm. Being an airborne virus we haven't seen before is one reason why the new coronavirus is so contagious.
Being a virus we haven’t seen before is one reason why the new coronavirus is so contagious and also why covering our cough is so important to prevent its spread. Photo: Getty Images.

“If you’re sick, don’t openly cough out into the air. Cough into a tissue and throw that tissue away, or cough into your elbow. Then wash your hands. ” Pastula said.

In addition, if a family member is sick in your home, try to isolate them within the home.

“People should come up with a plan to have an area of the home that is a relatively quarantined space so they’ve isolated themselves from the rest of the household. This room and bathroom are used for whomever is sick,” Pastula said.

“If you can find them a regular facemask, the sick person can use that to prevent the droplets from being coughed out farther than they would otherwise, limiting their spread,” he said.

How long can the coronavirus last on a surface?

“We don’t know exactly how long the virus can last on surfaces. Some preliminary data suggests it could last many hours to even a few days depending on the surface, but we need more data.” Pastula said.

A preliminary studied showed that the coronavirus could last for up to three days on certain surfaces, but it’s unclear whether the conditions in the lab would mirror conditions in the real world, where light, humidity, temperature and other factors can affect how the virus behaves.

Regardless, Pastula said it’s wise to clean surfaces that you touch frequently. The CDC recommends daily cleanings. Learn more here

Tyler agreed that it’s most important to think about where the virus is most prevalent: in the nose, mouth and throat of an infected person, rather than focusing on exactly how long the virus can last on a surface.

“When we think of human to human transmission, that is happening primarily through coughing and sneezing. Small, aerosolized particles can survive for some limited period of time on surfaces. But, most of the experts think the primary exposure, as best we can determine, is probably person-to-person not through an object you touch, like the remote control,” Tyler said.

Frequent hand washing and avoiding touching your face are the best ways to prevent the spread of the coronavirus, both Tyler and Pastula said.

How can I get information I can trust?

Medical experts advise people to be wary of random information they find online.

“There’s a lot of stuff on social media now that may be out of date, inaccurate, or misleading,” Pastula said. “My suggestion for everyone is to get your recommendations from the CDC (the Centers for Disease Control and Prevention) or from your state health department. They will have the most factual, up-to-date information.”

“Social media has its place, but you want the latest evidence-based recommendations in this rapidly changing situation. So go straight to the source. Go to the CDC and the CDPHE (Colorado Department of Public health and Environment) for the most up-to-date actionable information.”

About the author

Katie Kerwin McCrimmon is a proud Coloradan. She attended Colorado College thanks to a merit scholarship from the Boettcher Foundation and worked as a park ranger in Rocky Mountain National Park during summers in college.

Katie is a dedicated storyteller who loves getting to know UCHealth patients and providers and sharing their inspiring stories.

Katie spent years working as an award-winning journalist at the Rocky Mountain News and at an online health policy news site before joining UCHealth in 2017.

Katie and her husband, Cyrus — a Pulitzer Prize-winning photographer — have three adult children and love spending time in the Colorado mountains and traveling around the world.