As the number of people infected with COVID-19 continues to rise, scientists are working to better understand how the virus is spread.

One of their questions: How long can the new coronavirus that causes COVID-19 survive on surfaces like doorknobs and countertops, and how easily could someone get sick from touching those surfaces?

The answer isn't yet known for sure, but scientists assume the new virus behaves the same as other coronaviruses, such as those that caused previous outbreaks of Severe Acute Respiratory Syndrome, or SARS, and Middle East Respiratory Syndrome, also known as MERS.

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"While we don’t know for sure that this virus will behave the same way as SARS-CoV and MERS-CoV, we can use the information gained from both of these earlier coronaviruses to guide us," the Centers for Disease Control and Prevention (CDC) says on its website.

The World Health Organization has previously said those viruses can last at least two days on surfaces. Officials with the CDC have said coronavirus is short-lived on surfaces.

(MORE: Scientists Fear Quarantined Cruise Ship Passengers Could Spread Coronavirus When They Leave Ship)

A new study published last month in the Journal of Hospital Infection showed that coronaviruses like those that caused SARS and MERS could survive for up to nine days on surfaces that have not been disinfected, including metal, glass or plastic.

The study also showed that higher temperatures between 86 and 104 degrees can decrease survival of coronaviruses.

"Based on the current available data, I would primarily rely on the data from SARS coronavirus, which is the closest relative to the novel coronavirus – with 80% sequence similarity – among the coronaviruses tested," Dr. Charles Chiu, who was not involved in the study but is an infectious disease professor at the University of California, San Francisco, and director of the USCF-Abbott Viral Diagnostics and Discovery Center, told CNN. "For SARS coronavirus, the range of persistence on surfaces was less than five minutes to nine days."

Chiu added that further studies are still needed.

"However, it is very difficult to extrapolate these findings to the novel coronavirus due to the different strains, viral titers and environmental conditions that were tested in the various studies and the lack of data on the novel coronavirus itself," he said. "More research using cultures of the novel coronavirus are needed to establish the duration that it can survive on surfaces."

The CDC says COVID-19 is primarily spread through close contact – defined as 6 feet or less – with an infected person, specifically via droplets when an infected person sneezes or coughs.

"These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs," according to the CDC. "It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose or possibly their eyes, but this is not thought to be the main way the virus spreads."

Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, said in a press conference Friday that "some spread may happen by touching the contaminated surface and touching the eyes, nose and mouth. But remember, this does not last long on surfaces."

The CDC has also said there is little chance the virus could be spread through things like packages and mail.

Still, fear of the unknown is prompting extreme measures in China, where banks have been ordered to disinfect all cash before it is put into public distribution and cash transfers between provinces have been suspended.

Flu Insights with Watson helps people better assess and prepare for their flu risk, up to 15 days in advance, down to their ZIP code. Check your local risk in The Weather Channel app.

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