Jan. 20 (UPI) -- Chinese health officials said Monday a third person has died from a mysterious new virus as it spreads throughout the country.
Health officials in the central Chinese city of Wuhan said in a statement that a patient infected with the new virus died over the weekend, bringing the death toll to three after a 69-year-old man died Wednesday and a 61-year-old-man died on Jan. 9.
The disease, identified as a new coronavirus infection, is similar to the virus behind severe acute respiratory syndrome, better known as SARS, which killed hundreds of people in Hong Kong and mainland China from 2002 to 2003.
The World Health Organization said the initial patients first reported sick on Dec. 31 and it is believed the outbreak is connected to a seafood market now closed in Wuhan.
On Monday, WHO said it believes the primary source of the outbreak is animal though "limited human-to-human transmission" is responsible for the disease's spread.
The Wuhan Health Commission said it recorded 136 new patients suffering from pneumonia caused by the new coronavirus over the weekend, raising the total number of cases to 198.
"Currently 170 cases are still being treated in the hospital, of which 126 are mild, 35 cases are severe and nine cases are critically ill," the commission said. "They are all under isolation treatment at designated institutions in Wuhan."
It said 59 cases were reported on Saturday and 77 were reported on Sunday.
The news comes as health officials throughout China are dealing with patients falling ill with the new disease.
Officials confirmed two cases in Beijing and one in Shenzhen, where eight patients are currently in quarantine in connection to the disease. In Zhejiang, five people are reported to be in quarantine.
WHO said China has reported to it a total of 139 cases nationwide.
"For the first, there are novel coronavirus cases reported outside of Wuhan within China," WHO said on Twitter.
The increase in the number of reported cases over the weekend can be attributed to "searching and testing for cases outside Wuhan," the international health organization said.
"WHO is proposing studies on the novel coronavirus that can be done in China and elsewhere to better understand transmission, risk factors and where the virus is," it said.
The U.S. Centers for Disease Control and Prevention said it is working closely with WHO and has increased screening of passengers on direct and connecting flights from Wuhan to the three main ports of entry in the United States.
Meanwhile, health officials in South Korea on Monday confirmed the country's first case of the disease.
A Chinese woman suffering from fever and respiratory problems who arrived in South Korea via Incheon International Airport tested positive for the virus, Yonhap News Agency reported.
Korea's CDC said the woman had visited Wuhan, Hubei province, last week and was now being treated at a local hospital.
Japan and Thailand have also reported cases of the disease among people who recently visited Wuhan.