Cruise Ship Cases Show Symptom-free COVID-19 Patients Can Carry Virus for Weeks

By Reuters Staff

June 15, 2020

(Reuters Health) - Japanese doctors tracking cruise ship passengers and staff who became infected with the novel coronavirus but experienced no symptoms have found that most continued to remain symptom free but it took 15 days for 90% to clear the virus from their bodies.

The study, published online by The New England Journal of Medicine, did not directly assess how effectively the asymptomatic patients could spread the infection.

But among 32 cabinmates of the infected people who were also followed but did not initially test positive, eight tested positive for COVID-19 within 72 hours. Intriguingly, none developed symptoms.

The older the person, the longer it took for the infection to go away.

The data come from the British cruise ship Diamond Princess. Its 3,711 passengers and crew were quarantined by the Japanese government on February 3. Testing showed that 712 had been infected but 311, or 44%, had no symptoms.

The new report, led by Dr. Aki Sakurai of Fujita Health University, followed a subset of 128 passengers, cabinmates and crew taken to Fujita's Okazaki Medical Center for observation.

Ninety six were infected but asymptomatic when tested on the ship. Eleven of the 96 ultimately developed symptoms, typically within four days. One person was lost to follow-up.

But 84 of the 96 (88%) in this subset never developed symptoms.

Nine days after testing positive for COVID-19, the virus was still detectable in about half of those patients. By the 15th day, 10% still showed evidence of infection. It lingered in one patient for 21 days.

Among infected patients in their 40s, it typically took 7 days for lab tests to show the infection was gone. For those in their 70s, it was 12 days or longer, the researchers report in their letter to the Journal.

SOURCE: The New England Journal of Medicine, online June 12, 2020.