The Science Behind COVID-19

By Sara Bondell - March 25, 2020

As many of us know by now, coronaviruses are a group of closely related viruses that cause a wide range of illness, from a common cold to more serious diseases of recent years, such as SARS (Severe Acute Respiratory Syndrome).

COVID-19 is a “novel” form of the coronavirus, which means that it’s a completely new disease and has never been catalogued among other known viruses. Scientists are quickly working to gather data on the disease to investigate its origins, track its spread and come up with treatment options.

Here’s the science behind the pandemic:

Where it comes from

Most newly emerging viruses circulate in an animal habitat and then adapt and evolve to ultimately enter the human population. The source of COVID-19 is believed to be a market in Wuhan, China which sold both dead and live animals.

How quickly it spreads

Each virus spreads at a different rate, which scientists track by assigning a reproduction number, or R0. The rate is an important concept in epidemiology and is a critical part of public health planning during pandemics, including the 2003 SARS pandemic, 2009 H1N1 (swine flu) pandemic, the 2014 Ebola epidemic and now the COVID-19 pandemic.

For example, measles has one of the highest rates, with an R0 of about 15-18. This means one person with measles will infect 15 to 18 other people. On the other hand, the flu is less infectious, with an R0 of 1.3. Scientists are currently trying to nail down COVID-19’s reproduction number, but estimate it is somewhere between 2 and 3.

“Many viruses replicate very quickly,” said Dr. Jennifer Binning, a virologist at Moffitt Cancer Center. “They produce multiple copies of themselves and this helps them adapt to new situations and deal with different pressures such as jumping to a new host or developing drug resistance.”

COVID-19 is spread person-to-person between people in close contact with each other and through respiratory droplets produced when someone sneezes or coughs. People are more contagious while showing symptoms; transmission of the virus before symptoms present is possible but unlikely, according to the Centers for Disease Control.

“Just because you’re not showing symptoms does not mean that you are not infected,” said Binning. “As long as you’re infected that means the virus is replicating inside of you, and if you’re producing more virus then you’re in a position where you could transfer it to another human being.”

A new study published in the New England Journal of Medicine analyzed how long the virus that causes COVID-19 can live in the air and on surfaces. It was more stable on plastic and stainless steel than on copper and cardboard. Viable virus was detected up to 72 hours after application to plastic and up to 48 hours on stainless steel. On copper, the virus was not detected after four hours and it wasn’t present on cardboard after 24 hours. Researchers also concluded that transmission is possible through the air and fomite—objects such as clothes, utensils and furniture.

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"Just because you’re not showing symptoms does not mean that you are not infected,” said Binning. “As long as you’re infected that means the virus is replicating inside of you, and if you’re producing more virus then you’re in a position where you could transfer it to another human being."

- Dr. Jennifer Binning, virologist

Chinese researchers were able to quickly genetically sequence COVID-19 after the initial outbreak and identified two different strains of the virus. Scientists can now use that genetic information to track how the disease spreads.

“We know at this point the virus mutates approximately twice every month, so about once every 15 days,” said Binning. “Using this information along with known incubation periods, scientists are able to create a transmission map to essentially figure out if person A was responsible for infecting person B, who then went on to infect person C and so on.”

Cancer and COVID-19

While cancer patients are undergoing treatment, they are immunocompromised. When you don’t have a good immune system, it makes your body a perfect vessel for the virus to go in and replicate, completely uncontrolled.

Dr. John Greene, chair Moffitt's Infectious Disease Program
Dr. John Greene, chair of Moffitt's Infectious Disease Program

A study published in The Lancet Oncology is the first of its kind to focus on COVID-19 in patients with cancer. It found that while cancer patients are no more likely than the average person to be infected, they did have worse outcomes.

“There’s a three times greater risk of them dying from it than those without cancer,” said Dr. John Greene, chair of the Infectious Disease Program at Moffitt. “Cancer per say may not necessarily be a risk, but when you factor in immunosuppression, patients can catch all kinds of viruses and have a much higher risk of severe illness and death.”

Stopping the Pandemic

As COVID-19 continues to spread across the globe, containment now seems impossible. A vaccine to combat the virus could also be years away. So, when will the outbreak end?

Some epidemiologists are estimating up to 70% of the population will be infected with COVID-19. “If a large portion of the population does get it, then in theory we would build herd immunity,” said Binning. “Unfortunately, developing immunity in this way would be very costly and many unnecessary lives would be lost. This is why there are efforts underway to develop a vaccine quickly.”

As warmer weather descends across the U.S. in the coming months, some are hoping it will stop or at least slow the spread of the virus. Some viruses become less transmissible as temperatures and humidity rise, but there’s no proof this will be the case with COVID-19.

“Other coronaviruses have been shown to thrive in colder, drier climates,” Binning said. “However, COVID-19 is a novel virus and we honestly don’t know how the weather will affect it. We currently have outbreaks in locations where the temperature is well above 80 degrees so it is hard to know if or when the changing seasons will reduce the virus’s ability spread.”

The best thing people can do to stop or slow the spread of COVID-19 is practice social distancing and good hygiene practices like hand washing.

“The growth curve for COVID-19 is exponential,” said Binning. “With the current infection rates that we’re seeing in many of the other countries and in ours, the virus is doubling every three days. So, if you play that out, you have 1,000 infections on Monday, by Thursday you have 2,000, Sunday you have 4,000. That large growing increment is why we are taking this so seriously.  If we don’t address the problem early, then it can easily get out of hand leaving our healthcare system completely overwhelmed.”

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Sara Bondell Medical Science Writer 813-745-1353 More Articles

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