A patient suspected of suffering from pneumonia arrives at a hospital in the western Ukrainian city of Lviv on Tuesday. Urging its citizens not to panic, Ukraine on Monday closed down all schools nationwide for a week to avoid the spread of swine flu. (Sergei Grits/Associated Press)

People in the priority groups for the H1N1 vaccine in the northern hemisphere should receive the swine flu shot, the World Health Organization advised on Tuesday.

"Certainly, the fact that the vaccine isn't being used by those who would have access to it and who would be in priority risk groups is of concern, yes," WHO spokesman Gregory Hartl told reporters from the UN health agency's headquarters in Geneva.

Priority groups for the vaccine include:

• Health workers.
• Pregnant women, particularly in the second half of pregnancy.
• Those with medical conditions such as asthma.

"We have seen many, many instances of people in high-risk groups, such as pregnant women, who have very severe disease or outcomes," Hartl said. "These outcomes could be, in all likelihood, avoided if one were to get vaccinated."

The vast majority of people with flu recover fully at home. Deaths among children infected with H1N1 are rare. But the virus is hitting children harder than seasonal flu, which is most dangerous for people over the age of 65.

At least 5,712 people worldwide have died from the swine flu virus, WHO said.

There are signs that influenza is becoming widespread across the temperate areas of the northern hemisphere, which is entering the winter flu season, Hartl said.

Investigating Ukraine's outbreak

In Ukraine, the number of deaths from a flu-like illness has climbed to 71 since the start of a flu outbreak last week in the western city of Ternopil, Prime Minister Yulia Tymoshenko said.

Ukraine's ministry of health said the country has recorded more than 250,000 cases of flu-like illness, with 235 patients needing intensive care.

At the request of Ukraine's government, the WHO has sent a team of nine experts to the East European country. They will investigate whether the same strain of H1N1 influenza A virus that caused the current global swine flu pandemic is to blame for Ukraine's flu outbreak.

Ukraine lacks an H1N1 vaccination program, and the government has shut down parliament for a week and banned public gatherings as a precaution.

"By closing schools and cancelling mass gatherings in the early stages of an event … you can slow down the transmission of the virus," Hartl told the Associated Press. "So far, there is only one confirmed death [from H1N1 in Ukraine]."

Russia and Slovakia have also tightened their borders with Ukraine. Slovakia closed two of its five border crossings with Ukraine. Russia's health ministry said it would examine anyone crossing the border from Ukraine and quarantine anyone showing severe symptoms.

Some Ukrainian health officials and medical experts have accused the government of exaggerating the outbreak ahead of January's presidential elections, given that the total number of flu deaths has dropped by 10 per cent compared with last year, the UNIAN news agency quoted Deputy Health Minister Vasily Lazorishinets as saying.

Elsewhere on Tuesday, South Korea raised its H1N1 alert status to the highest level. The virus has killed 42 people in the country.

The mortality rate was "not so much different from seasonal flu," at 0.3 per cent, health ministry official Park Ha-jeong said, stressing there was "no need to fear or worry about the disease".

With files from The Associated Press