BEIJING — Here are the latest developments on COVID-19 in China:

— Chinese health authority said on May 15 that it received reports of four new confirmed COVID-19 cases on the Chinese mainland on May 14.

All the four cases were domestically transmitted and reported in northeastern Jilin province, the National Health Commission said in its daily report.

— Jilin provincial health commission said the four new cases reported on May 14 were close contacts of earlier confirmed cases in the cities of Shulan and Jilin.

— No new confirmed COVID-19 cases were reported in Central China's Hubei province on May 14, the provincial health commission said on May 15.

By the end of May 14, Hubei still had six confirmed COVID-19 cases, all in the provincial capital of Wuhan, including one in severe condition and one in critical condition.

— Hubei's capital city of Wuhan will arrange nucleic acid tests for all residents who have not been tested before, in order to better know the number of asymptomatic cases of the novel coronavirus.

The decision was made as the hard-hit city continued to report daily increases in asymptomatic infections, which raised concerns among the public.

— The second phase of clinical trials for COVID-19 vaccines is expected to be completed successively beginning in July, and no major adverse reactions from the trials had been reported so far, a Chinese official said on May 15.

— An NGO in Southwest China's Sichuan province has donated a batch of medical supplies to aid the fight against COVID-19 in Costa Rica, the provincial foreign affairs office said on May 15.

The Sichuan NGO Network for International Exchanges said they donated more than 30,000 surgical masks to the Costa Rican Association for Friendship with China and sent them to Costa Rica on the night of May 14.

— A team of Chinese scientists has found strong evidence that the novel coronavirus is of natural origin and not leaked from a laboratory.

The researchers made the discovery by analyzing a close relative strain of the virus, denoted RmYN02, which is derived from bats and shares a high degree of identity with the novel coronavirus in the 1ab region of the genome.

— Officials and medical experts in Central China's Hunan province on May 14 shared anti-epidemic experience with their counterparts in Santo Domingo, capital of the Dominican Republic.

Via a video conference, Chinese officials and experts answered a host of questions on COVID-19, including what major measures China has taken against the epidemic, how to disinfect public places, as well as how to meet the citizens' basic needs amid the epidemic.

— A hospital in Guangzhou, capital of southern China's Guangdong province, has shared experience of its fight against COVID-19 through a video conference with medical workers from hospitals in Ukraine.

Medical staff from the Guangzhou Eighth People's Hospital on May 14 gave a livestreaming lecture to and answered questions from seven hospitals in Kiev, capital of Ukraine, including how Guangzhou managed the treatment of COVID-19 patients, especially those who are pregnant or have HIV.

— Provincial-level regions in China have donated more batches of medical supplies to foreign regions to aid their fight against COVID-19.

On May 15, shipments of medical supplies donated by Northwest China's Ningxia Hui autonomous region left for Russia's Tula, Japan's Shimane Prefecture and Romania's Harghita county to help with the local coronavirus fight.