As cases passed the 70,000 mark today, China published a detailed picture of its COVID-19 outbreak, which now shows signs of declining; however, officials warned cases could rebound as people return to work and school after the extended Lunar New Year break.

In other developments, the number of infected people on the Diamond Princess cruise ship in Japan continued to soar, as infections were detected in 14 Americans who were just evacuated from the ship.

Large epi study notes 14% severe rate

China's report on the outbreak's epidemiologic patterns covers all COVID-19 cases reported through Feb 11 and appears in the China CDC Weekly, a publication that is similar to the US Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.

The team analyzed more than 72,000 patient records, of which 44,672 were lab-confirmed cases, 16,186 suspected cases, 10,567 clinically diagnosed cases, and 889 asymptomatic cases. Of the confirmed cases, 80.9% cases were mild, and the vast majority (86.6%) of confirmed cases were in people ages 30 to 79 years old.

About 14% of the illnesses were severe, which included pneumonia and shortness of breath, and about 5% have critical disease, marked by respiratory failure, septic shock, and multi-organ failure. The overall case fatality rate was 2.3%, and of 1,023 deaths included in the study, the majority were in people age 60 and older or those with underlying medical conditions.

Epidemiologic curve analysis shows a common source pattern in December, which shifted to a propagated source pattern starting in early January, which the researchers said might reflect several zoonotic events at the outbreak market in Wuhan. Around Jan 23 to Jan 26, the epidemic peaked and began to decline, according to the data.

Though 1,716 healthcare workers were infected in the outbreak, 5 of them fatally, there is no evidence of super-spreader events in healthcare facilities caring for COVID-19 cases, the group wrote. Those events were hallmarks of outbreaks involving severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome coronavirus (MERS-CoV). So far, it's not clear if the difference is due to the virus or prevention tactics, they noted.

China's massive control measures, which started on Jan 23 with limiting travel in and out of Wuhan, slowed China's epidemic and its spread to the rest of the world, the authors note. But they warn that officials need to prepare for the epidemic to rebound when huge numbers of people in China return to work and school.

Caution urged in interpreting outbreak decline

At a media telebriefing today, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus, PhD, said the new data from China gives health officials a better understanding about the affected age range, the severity of the disease, and the mortality rate, which he said helps the WHO deliver evidence-based guidance to countries.

However, he said the report's indication of a decline in cases should be interpreted with caution. "Trends can change as new populations are affected," he said. "It's too early to tell if this reported decline will continue. Every scenario is still on the table."

Tedros said relatively few cases have been reported in children, but more research is needed to understand why. Though the new report fills in some gaps for understanding the outbreak, others remain. He added that the international expert team is now on the ground in China to answer more questions and to get an even clearer picture of the outbreak.

China's National Health Commission today reported 2,048 new cases, a slight increase from the 2,009 it reported yesterday. It also reported 628 fewer severe cases as it adjusts those totals and 105 more deaths. The country's totals now stand at 70,548 cases, 10,644 severe cases, and 1,770 deaths.

Cruise ship cases grow by 99

Japan's health ministry today reported that 99 more people on the Diamond Princess cruise ship have tested positive, raising the total to 454. The ship has been quarantined in Yokohama port since Feb 3.

Meanwhile, the US State Department said it evacuated more than 300 US citizens and their family members who had been on the Diamond Princess, and all were evaluated by medical officials from the Department of Health and Human Services and deemed asymptomatic and fit to fly.

However, between getting off the ship and heading for the airport in Japan, US officials learned that 14 passengers who had been tested 2 or 3 days earlier were positive for COVID-19. They were moved to a specialized part of the aircraft and isolated according to standard protocol.

The whole group flew back to the United States, with passengers slated to arrive at either Travis Air Force Base in California or Joint Base San Antonio in Texas.

In other developments in Japan, the country's health ministry reported two more local cases, one involving a health ministry official who worked as a liaison on the Diamond Princess and the other a nurse who worked at a hospital near Tokyo, where she took care of a woman in her 80s who died from the disease, Kyodo News reported today.

Singapore, UAE report more cases

Singapore's health ministry today reported 2 more cases, raising its total to 77. The patients include an individual who was evacuated from Wuhan on Feb 9 and a person who is a contact of an earlier case.

The United Arab Emirates (UAE) health ministry yesterday reported 1 more COVID-19 case, which involves a 37-year-old Chinese man. The infection brings the UAE's total to 9, of whom 3 have recovered and 6 are still receiving treatment, 1 of them in an intensive care unit.

Gene analysis debunks lab-made claims

In a preprint publication yesterday, an international group of virologists detailed the evidence that the virus that causes COVID-19 is not lab made or artificially manipulated.

Based on their analysis of the genome, they described its notable features and scenarios that likely led to its evolution. They proposed two scenarios: natural selection in a host animal before the virus jumped to humans, or natural selection in humans following transmission from animals to people.

They also looked at whether selection during passage in culture could have produced the same genetic features they observed.