US researchers have revealed traces of the virus that causes the COVID-19 illness remained present on surfaces of a cruise ship for up to 17 days.
More than 700 passengers, including several Kiwis, contracted the respiratory illness on the Diamond Princess cruise ship in February, as the virus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) was in the infancy of its global spread.
The ship docked in Yokohama, Japan with the roughly 3700 passengers and crew in quarantine. At the time, it was the largest outbreak outside of China, where the virus originated.
A new paper published on the Centers for Disease Control and Prevention's (CDC) website sheds new light on how cruise ships can become hotspots for virus outbreaks.
"Cruise ships are often settings for outbreaks of infectious diseases because of their closed environment, contact between travellers from many countries, and crew transfers between ships," it says.
"On the Diamond Princess, transmission largely occurred among passengers before quarantine was implemented, whereas crew infections peaked after quarantine."
The researchers note that 17.9 percent of infected people aboard the ship never developed symptoms. That could "partially explain the high attack rate among cruise ship passengers and crew". About 46 percent were asymptomatic at the time of testing.
The paper also said that ribonucleic acid (RNA) of the SARS-CoV-2 virus was found on various surfaces in the ship's cabins up to 17 days after they were vacated, but before disinfection procedures had been conducted. This was found in both the cabins of symptomatic and asymptomatic patients.
"Although these data cannot be used to determine whether transmission occurred from contaminated surfaces, further study of fomite transmission of SARS-CoV-2 aboard cruise ships is warranted."
Canada's Global News spoke to Alon Vaisman, an infection control physician at the University of Toronto, who called RNA "the basic building block of the genetic code for the virus". He said just because RNA was detected, that doesn't mean the virus was alive at the time.
Microbiologist Jason Tetro told the outlet that coronaviruses last on a surface for nine days in a lab.
"So this identification does not have any impact on transmission on the risk for humans - it just simply means that, at one time or another, the virus happened to be on their ship," he said.
A study from earlier in March published in the The New England Journal of Medicine found SARS-CoV-2 stayed viable in aerosol for three hours, on copper for four hours, on cardboard for up to a day, and on plastic and stainless steel for up to three days.
How can I protect myself?
- avoid touching the mouth, nose and eyes with unwashed hands
- washing your hands before eating
- carrying a hand sanitiser at all times
- being particularly mindful of touching your face after using public transport or going to the airport
- carry tissues at all times to cover the mouth and nose when coughing or sneezing (then dispose of it)
- not eating shared or communal food
- avoiding shaking hands, kissing cheeks
- regularly cleaning and sanitise commonly used surfaces and items, such as phones and keys
- avoiding close contact with people suffering from or showing symptoms of acute respiratory infection
- seeking medical attention if you feel unwell.
An explainer on protecting yourself from coronavirus can be found here. Full information can also be found at Covid19.govt.nz
The Ministry of Health is reminding the public to get in touch with Healthline on 0800 358 5453 if they have symptoms or concerns.