Six days after two cats were confirmed to have been infected with avian influenza, commonly known as bird flu, at an animal shelter in Seoul, an additional cat was confirmed to have contracted the virus at an animal shelter in another district of the city, the Agriculture Ministry said on Tuesday.

A cat at an animal shelter in Gwanak-gu died after showing respiratory symptoms and receiving treatment. An in-depth test found it was infected with a highly pathogenic H5N1 bird flu strain, according to the ministry.

Two cats died in Yongsan-gu last week, marking the first two bird flu cases detected in mammals since 2016.

As all the infected cats so far have been strays, experts believe that they contracted the virus through contact with wild birds or feces in the wild, according to the officials.

Highly pathogenic bird flu is an acute respiratory infectious disease caused by some viral strains of bird flu. It can also be spread to various species of mammals, including humans.

The bird flu type detected in Korea is the H5N1 influenza virus. H5N1 is highly contagious among birds, including chickens, and has a nearly 100 percent case fatality rate.

While bird flu can be transmitted to humans, such cases are rare and mainly affect those with close contact to birds, such as poultry farm workers or those with small flocks of birds at home. Since 2003, more than 20 countries have reported more than 860 human infections with H5N1 bird flu viruses to the World Health Organization. Among them, 457 were fatal, making for a 53 percent case fatality rate.

However, the human mortality rate of the bird flu strain prevalent in Korea is not high. “The virus prevalent in Korea is a subspecies among H5N1, and the fatality rate in human infections is around 10 percent,” an official from the Korea Disease Control and Prevention Agency said.

Furthermore, the quarantine authorities also believe that the possibility of human infection is not very high this time, as there have been no reports of H5N1 spreading from birds to humans through cats or other mammals around the world.

The Seoul Metropolitan Government sent an emergency text message on Monday cautioning people to avoid touching animal carcasses or feces, and to wash their hands frequently.

The disease control agency and local government are looking into people who came into close contact with the infected cats, categorized as “high-risk.” Such individuals will be closely monitored for 10 days from the last day of contact. So far, no person in contact with the cats have shown symptoms, the authorities said.

Meanwhile, the Agriculture Ministry has decided to take preventive measures such as disinfection and access control within 10 kilometers of the area surrounding confirmed bird flu cases in cats. It will also conduct a bird flu infection check on stray cats in Seoul through Aug. 20. In addition, the Environment Ministry will conduct a fact-finding survey focusing on nearby migratory bird habitats.