SYDNEY, June 27 (Xinhua) -- The Papua New Guinea (PNG) Department of Health, along with the World Health Organization (WHO) are continuing to respond to a potentially deadly outbreak of the devastating poliovirus, local media reported Wednesday.

The PNG Department of Health and the WHO have launched an emergency immunization campaign to stop the spread.

Confirmed on Monday in the South Pacific nation's second largest city, Lae, the infectious disease is known to cause lifetime paralysis in children.

"We are deeply concerned about this polio case in Papua New Guinea, and the fact that the virus is circulating," PNG's National Department of Health secretary Pascoe Kase said.

"Our immediate priority is to respond and prevent more children from being infected."

Although the country was officially declared "polio-free" back in the year 2000 and has not had any reported cases since 1996, a six-year-old boy was admitted to hospital in April this year experiencing "lower leg weakness."

Over time his condition worsened to paralysis and in May, medical authorities confirmed the boy was suffering from a vaccine-derived poliovirus infection.

One month later on June 25, the community's worst fears were realized when the U.S. Centers for Disease Control and Prevention found the same virus in two other children's stool samples.

With clear evidence the disease has spread in the Lufa Mountain settlement area where the boy lived, the WHO have began a large-scale immunization campaign and made 500,000 U.S. dollars available to strengthen surveillance systems that can detect the virus early.

"We will continue to support the government to ensure children are protected," WHO representative in Papua New Guinea Luo Dapeng said.

"Since the detection of poliovirus in April, WHO has been working with the government on the investigation, laboratory confirmation, enhanced surveillance and response activities."

Predominantly spread in unsanitary conditions, poliovirus is often transferred through contaminated food and water.

According to the WHO, the vaccination rate in Morobe province where the city of Lae is located, is just 61 percent.