It has been nearly a month since four-year-old Edgar Hernandez, the first recorded person to show strains of the new virus, was taken ill on April 2. The U.S. was reporting two cases of swine flu by April 17 - nearly two weeks ago - and the first cases to be reported in the UK came on April 27, ten days after that.

This morning the World Health Organisation said on its website that as of 6am GMT, swine flu had infected 331 people in 11 countries, killing ten of them. Other estimates of the infections and deaths are higher - for instance Mexico says up to 176 people have died there and the authorities have confirmed 12 deaths.

However, despite the variations, the numbers are still relatively small - and they don't seem to be multiplying by hundreds and hundreds (yet).

Between 3 and 5 million people experience severe illness due to regular, seasonal flu around the world each year, and between 250,000 and 500,000 die as a result.

In the United States annually between five per cent and 20 per cent of the population becomes ill from the flu and 36,000 people die —a mortality rate of between 0.24 per cent and 0.96 per cent, reports have claimed.

The current mortality rate for swine flu is between 0.06 per cent and 0.24 per cent, the Los Angeles Times has reported - making it less lethal than the yearly bout of influenza.

Keiji Fukuda, the WHO's acting assistant director-general, said that swine flu appeared very similar to normal seasonal flu, a disease that is rarely fatal for healthy adults but can kill the elderly and infirm.

'Let's not lose track of the fact that the normal seasonal influenza is a huge public health problem that kills tens of thousands of people in the U.S. alone and hundreds of thousands around the world,' Dr Christopher Olsen, a molecular virologist who studies swine flu at the University of Wisconsin School of Veterinary Medicine, told reporters.

The mortality rate and rate of transmission could change - for better or for worse. Flu viruses are known for being unpredictable, and from the beginning scientists have warned that this strain could mutate at any point - becoming either more or less deadly.

The WHO's director general Margaret Chan has reinforced this several times. Echoing other infectious disease experts, and drawing on her experience fighting SARS and bird flu outbreaks as health director of Hong Kong, she said viruses such as the H1N1 swine strain needed to be closely watched in case they worsen.

'We learn from previous pandemics. Pandemic virus is precarious, unpredictable, and will take us by surprise,' she told reporters at the WHO's headquarters yesterday.

Fukuda said it was not yet clear whether swine flu would turn into a mild or severe pandemic, raising the possibility that the virus could have more serious effects as it continues to permeate new communities or as climate conditions change.

There were three pandemic flu outbreaks in the 20th century - in 1918, 1957 and 1968 - known respectively as Spanish, Asian, and Hong Kong influenza. An estimated 50 million people died in the first outbreak, about 2 million in the second and between 1 and 3 million in the third.

'In the 1918 pandemic, the first wave was mild, but by fall, the second wave killed many people. So whichever way this virus swings, we can't possibly know,' said Guan Yi, a microbiologist at the University of Hong Kong.

'At this point, chances are it will be mild, but we can't rule out it will turn virulent. And even if it turns milder, it can still kill, depending on the kind of person it infects.'

The experts are understandably cautious - but as more and more evidence comes in, authorities are starting to hope we could avoid a worst-case scenario in this particular global pandemic.

Chan acknowledged that the disease may well cause more discomfort than death, noting that many patients infected in the United States have recovered on their own and without medicine.

'It is possible that the full clinical spectrum of this disease goes from mild illness to severe disease. We need to continue to monitor the evolution of the situation to get the specific information and data we need to answer this,' she said.

'There may be a possibility that the virus will die out and stop, and that would be the best for us. But it can turn the other way.'

Despite the trickle, the WHO is expected to raise the alert level to six within days, declaring a global pandemic. Mexico has partially shut down its economy and begged citizens to stay in their homes, and U.S. Vice President Joe Biden said on national television that he has warned his family to stay off commercial airliners and the subway.

Perhaps the deluge simply hasn't yet begun.

In the meantime, though, the WHO's own guidance to people who suspect they have been infected with swine flu is essentially the same as advice for seasonal flu care.

Its website's 'frequently asked questions' about the virus tell people who have a high fever, cough or sore throat to rest and take plenty of fluids, wash hands frequently, and avoid work, school or crowds as much as possible.