The threat of a flu pandemic has gripped the world, as a virus that is thought to have killed more than 100 in Mexico spread to the United States and as far as Canada and possibly Israel and New Zealand.

No deaths have occurred outside Mexico from the new strain of swine flu but 20 cases have been identified in the United States and six in Canada.

The authorities say that none of those infected are seriously ill. However, they also believe more infections will be discovered in the coming days. Six cases have been confirmed in neighbouring Canada.

Swine flu is characterised by a sudden fever, muscle aches, sore throat and dry cough. Victims of the new strain have also suffered from vomiting and diarrhoea.

Epidemic in Mexico
In Mexico, where the outbreak began, the probable death toll from the epidemic is now more than 100. The authorities have announced that none of the 1300 other people originally thought to have been infected are suffering from the virus.

In a number of other countries, such as New Zealand, France, Israel and Spain, there are suspicions that some individuals have been infected, but none of these suspicions have so far been confirmed.

World better prepared
The World Health Organisation says the world is now better prepared than in previous years to combat a possible pandemic. Following the deadly outbreaks of Severe Acute Respiratory Syndrome (SARS) six years ago, many countries have now built up their stocks of vaccines.

Nonetheless, the WHO has declared the flu a "public health emergency of international concern" that could become a pandemic, or global outbreak of serious disease. That could cost trillions of dollars to a world economy already in its worst crisis in decades.

No panic in the Netherlands
An official for Amsterdam's Schiphol airport says the authorities do not see a need to take extra measures in connection with the swine flu outbreak in Mexico. KLM has a daily flight to Mexico City. The airline says departing passengers are already filling in a form about the state of their health.

The Erasmus Medical Centre in Rotterdam says it is not concerned about the virus. So far, no cases have been reported in the Netherlands. If any cases are reported, patients will be sent to the centre.