South Korea's health ministry has confirmed two people have died from Middle East Respiratory Syndrome (MERS), the country's first fatalities from the virus.

A 58-year-old woman, who had been treated as a suspected case of MERS, died of acute respiratory failure on Monday and tests later came back positive for the virus.

The second victim was a 71-year-old man, who had been on respiratory support with a history of kidney ailments.

The ministry confirmed 25 people have now been diagnosed with MERS, the emergence of which has triggered widespread public alarm.

MERS is considered a deadlier but less infectious cousin of Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people after it appeared in Asia in 2003.

CSIRO research scientist Gary Cremari told The World Today that not much was known about the disease.

"Look there's still … probably more unknown than there is known," Mr Cremari said.

"We certainly know that the original outbreaks occurred in the Middle East, we're certain that that's still the focal point of ongoing international infections although it is known that the virus probably exists in other camel populations elsewhere in the world."

Mr Cremari has been studying the virus at the Australian Animal Health Laboratory in Geelong, partly to determine if Australian camel populations have been affected.

He said that despite the outbreak in North Asia, health measures to contain MERS had been strong.

"All of the health workers across the world are closely monitoring for MERS and as soon as a case is identified, there's notification and so there is a strong containment going on which really is our best first line defence against the virus," he said.

"But it is possible that visitors to the Middle East, particularly that comeback to Australia, may well be infected but they pose a limited risk to the population more generally."

More than 20 countries have been affected by the virus, which has no known cure or vaccine, with most cases in Saudi Arabia where it has claimed more than 400 lives since 2012.

Government slams MERS response as 'insufficient'

South Korea's first case was reported on May 20 and the health ministry on Monday said that the 682 people who were exposed directly or indirectly to the virus have now been quarantined or put under special observation.

Authorities are considering a travel ban for those confirmed to have contracted the virus.

MERS facts Middle East Respiratory Syndrome Coronavirus is known as MERS and MERS-CoV

Middle East Respiratory Syndrome Coronavirus is known as MERS and MERS-CoV All recorded cases can be traced back to the Middle East

All recorded cases can be traced back to the Middle East Dromedary camels are thought to be the source of infection

Dromedary camels are thought to be the source of infection The virus can be spread person-to-person

The virus can be spread person-to-person Symptoms include fever, cough, shortness of breath and breathing difficulties

Symptoms include fever, cough, shortness of breath and breathing difficulties Severe cases can have a rapid onset of respiratory illness, like pneumonia

Severe cases can have a rapid onset of respiratory illness, like pneumonia There is no vaccine to prevent the virus Source: health.gov.au

The South Korean outbreak is the largest among countries outside the Middle East and president Park Geun-Hye has disparaged health officials over their "insufficient" response to the outbreak.

"Early measures were a bit unsatisfactory to firmly block MERS spreading into our society," South Korean president Geun-Hye said.

"I hope that the joint counter-measure team puts all its efforts into this and will closely co-operate with local governments."

Acting prime minister Choi Kyung-Hwan vowed "all-out Tuesday efforts" to curb the spread and ease "growing panic" among South Koreans.

"People believe that the health authorities' response has been inefficient and poor," he said in an emergency meeting with top health officials.

"We should use all our national resources to alleviate their concerns."

Health officials accepted criticism for allowing an infected man to travel to China last week despite warnings from doctors.

"We had a case in which a patient who should have been quarantined at home ended up going abroad to a third country so we'll all do our best to ensure this does not happen again by strongly demanding the implementation of strict measures," South Korean public health chief Kwon Jun Wook said.

The 44-year-old left on a business trip on Tuesday, a day after his father was diagnosed with the virus, and on Friday was confirmed to have been infected himself.

The man flew to Hong Kong before travelling on to the Chinese city of Huizhou, where he is being treated under quarantine.

The current outbreak has been traced to a 68-year-old man diagnosed after returning from a trip to Saudi Arabia.

The World Health Organisation said last week there had been no sustained human-to-human spread in South Korea, and that it was not recommending screening of passengers or the imposition of travel or trade restrictions.

ABC/wires