South Korea has confirmed its third Zika virus infection, local health authorities said Friday, raising fears about the rapid spread of the mildly contagious virus throughout the country.

The brother of a man diagnosed with the infection two days earlier has tested positive in a urine test for the mosquito-borne virus, the Korea Centers for Disease Control and Prevention (KCDC) said.

The 21-year old man, however, was not categorized as a confirmed Zika patient as his blood test was negative and he has no typical symptoms like muscle pain and skin rashes.

"He was infected with Zika virus but has no symptoms," said a KCDC official. "There is slim possibility that he caught the virus through a mosquito bite given his negative blood test result."

The man, who joined the Army on Tuesday to serve his two-year mandatory military service, has been admitted to a military hospital near Seoul for further medical treatment, according to the KCDC.

He traveled in the Philippines with his 20-year-old brother from April 10-14, when the younger man was infected with the virus.

On Wednesday, the younger brother was confirmed to be the country's second Zika patient after showing flu-like symptoms upon his return from the Philippines. He said he was bitten by a mosquito during his vacation.

The latest case raises the number of confirmed infections in South Korea to three. Last month, a 43-year-old man was confirmed as the first case of the virus in the country. The man reported being bitten by a mosquito while traveling in Brazil.

The latest Zika cases have raised concerns over a widespread epidemic in South Korea just a year after an outbreak of the Middle East Respiratory Syndrome (MERS).

The respiratory disease, that was first confirmed in May last year, claimed 38 lives before the government officially declared the country free of MERS in December last year.

Fears of a full-scale inland epidemic had weighed heavily on the economy, dragging down domestic consumption and reducing foreign visitors.

Months ahead of the Brazil Summer Olympics, the World Health Organization declared the Zika virus outbreak a global emergency.

Zika was first discovered in Africa, and has spread to parts of Asia and Latin America, including many Caribbean countries and Brazil. In Asia, China and Japan have reported a few confirmed cases. (Yonhap)