The number of swine flu cases worldwide has reached more than 77,000, including 332 deaths, says the World Health Organization.

The current strain of H1N1 influenza A virus has been circulating in several countries since it first appeared in Mexico in April.

Canada ranks No. 4 of all countries with reported cases of swine flu, according to official WHO cumulative totals released Wednesday.

In Canada, the latest data shows 25 people have died from the virus, and 7,983 cases have been reported.

The U.S. has the greatest number of cases reported in any single country, 27,717, with 127 deaths.

Mexico ranked second by country in terms of cases, with 116 deaths and 8,680 people infected, the WHO showed in the country-by-country breakdown.

Most cases are mild

Like any other flu, swine flu is a respiratory infection. It exploits a weakened immune system to attack major organs, especially the lungs. Most cases are mild and require no medical treatment.

The common flu sends about 20,000 Canadians to hospital each year. The Public Health Agency's website says between 4,000 and 8,000 Canadians can die of influenza and its complications annually, depending on the severity of the season.

Meanwhile, the British government on Thursday said health officials would stop liberally giving out Tamiflu to all cases and their contacts.

Britain's Health Secretary Andy Burnham told the House of Commons the antiviral drug would only be used to treat patients.

Many experts have criticized Britain's approach to the outbreak for wasting resources and drugs.