Washington - The number of human swine influenza cases in the United States increased to 64 Tuesday in five states, the US Centres for Disease Control and Prevention (CDC) said. The worst-affected was New York City, with 45 cases, while California reported 10 cases. There were 6 cases in Texas, 2 in Kansas and 1 in Ohio.

Those who have fallen ill in the US range in age from 7-54 years, with a median age of 16 years. There have been no deaths in the US.

Geneva - World Health Organization officials reiterated Tuesday that travel restrictions would not help stem the spread of the swine influenza virus, which was possibly spreading in the form of human-to-human transmission. "Border controls don't work, screenings don't work," said spokesman Gregory Hartl, speaking to reporters in Geneva. "Travel restrictions do not help."

The incubation period of the virus, which could be for up to six days, as well as the widespread nature, would make spot checks at airports, for example, ineffective.

Vienna - One Austrian woman was "likely" infected with swine flu and four others are suspected of having the same illness, Austrian Health Minister Alois Stoeger said Tuesday. All of the five had recently been to Mexico, the centre of the outbreak, the minister said at a press conference.

The most likely case is that of a 28-year-old woman in Vienna, who returned last week from a trip to Guatemala and Mexico, Vienna's chief health official Karin Spacek said.

Geneva/Brussels - Health experts appealed for calm Tuesday as the number of confirmed human infections from swine flu in Europe rose to four and governments sent out contradictory signals on how to deal with the spread of the virus. "Nobody should underestimate the situation, but there is no reason to panic either," Androulla Vassiliou, the European Union's health commissioner, said in Brussels.

As of Tuesday afternoon, four cases of swine flu had been confirmed in Europe - two in Britain and two in Spain.

Washington, Apr 28: While there have been a number of outbreaks of the new strain of swine flu, there also have emerged a whole gamut of misinformation. Now, scientists have elaborated exactly what one needs to know about this new epidemic.

Infectious disease expert Charles Ericsson, M. D., professor of internal medicine and director of Travel Medicine at The University of Texas Medical School at Houston, has answered some questions regarding swine flu, which are as follows:

1. How do symptoms of swine flu differ from other types of flu?

Mexico City, Apr. 28: The World Health Organization has raised the alert level in relation to the `Swine Flu’ epidemic to Phase 4, meaning there is sustained human-to-human transmission of the virus causing outbreaks in at least one country.

On Monday, the alert was raised above Phase 3.

Putting an alert at Phases 4 or 5 signals that the virus is becoming increasingly adept at spreading among humans.

Phase 6 is for a full-blown pandemic, characterized by outbreaks in at least two regions of the world.