TORONTO -- A cruise ship that saw scores of Canadians quarantined off the coast of Japan still had traces of COVID-19 some 17 days after passengers disembarked, according to a new study from the U.S. Centers for Disease Control.

The research looked at the efforts by health authorities in Japan and the U.S. to contain the spread of the coronavirus onboard the Carnival-owned Diamond Princess, which was quarantined for nearly four weeks near Yokohama, and the Grand Princess, which docked at Oakland, California.

“SARS-CoV-2 RNA was identified on a variety of surfaces in cabins of both symptomatic and asymptomatic infected passengers up to 17 days after cabins were vacated on the Diamond Princess but before disinfection procedures had been conducted,” the study authors note, citing personal correspondence from Takuya Yamagishi at the National Institute of Infectious Diseases.

RNA or ribonucleic acid is one of the three major biological macromolecules that are essential for all known forms of life, including viruses like COVID-19.

“Although these data cannot be used to determine whether transmission occurred from contaminated surfaces, further study of fomite transmission (objects that can carry infection) of SARS-CoV-2 aboard cruise ships is warranted,” the CDC authors wrote.

Despite a number of studies, there is still no definitive timescale for how long the coronavirus can live on surfaces.

According to the World Health Organization, COVID-19 is transmitted through small droplets from the nose or mouth, which are spread when a person with the virus coughs, sneezes, or exhales. These droplets land on objects and surfaces around the person.

A study recently published in the New England Journal of Medicine suggests that traces of the virus are detectable for up to four hours on copper, 24 hours on cardboard and up to two to three days on plastic and stainless steel. 

The Diamond Princess and Grand Princess had more than 800 COVID-19 cases, including 10 deaths.

For much of February, the largest cluster of COVID-19 cases outside China were on the Diamond Princess.

Last week, a Canadian died in Japan from complications related to COVID-19, Foreign Affairs Minister Francois-Philippe Champagne tweeted on Friday.

Global Affairs Canada confirmed to CTV News that the individual was a passenger on the Diamond Princess.

Of the 256 Canadians aboard the Diamond Princess, more than 40 tested positive for the virus and were taken to hospital in Japan. The remaining 129 Canadians were repatriated and sent to quarantine at Canadian Forces Base (CFB) Trenton for 14 days.

Canadian passengers onboard the Grand Princess cruise ship off California were also sent to CFB Trenton after cases of COVID-19 were identified there.

“More than 800 cases of laboratory-confirmed COVID-19 cases occurred during outbreaks on three cruise ship voyages,” the CDC study states.

“Transmission occurred across multiple voyages from ship to ship by crew members.”

The Canadian government has advised against cruise ship travel until further notice.

- With files from’s Sarah Turnbull and Nicole Bogart