Experts warn of dangers of swine flu with almost 10,000 now infected, forecasts 4.9 billion doses needed

The latest figures from the World Health Organisation (WHO) has the worldwide influenza A H1N1 (swine flu) tally fast approaching 10,000 human cases.

United Nations Secretary-General Ban Ki-moon has cautioned people to remain vigilant against swine flu as the number of cases has risen by more than 1,000 since Monday with 9,830 infections now in 40 countries, including 79 deaths.

The UN chief has warned that previous pandemics had shown flu outbreaks could start mild and worsen which is why the world must remain vigilant and alert to the warning signs.

Though the WHO has been reluctant to declare the outbreak a full scale flu pandemic because of the panic which might ensue, anxiety about the spread of the virus - especially in Asia and the Americas continues. Japan has now had 193 swine flu infections and closed more than 4,000 schools, colleges and kindergartens in order to slow the spread of the virus.

The WHO assembly opened this week amid pandemic fears and Ban Ki-moon has reportedly held talks with some of the world's biggest pharmaceutical companies on the development of a swine flu vaccine.

It is thought that around 30 vaccine makers from 19 industrialised and developing countries were invited to the discussions, which focused on the cost of the vaccine and its availability in the most vulnerable poor countries.

Ban told the WHO's assembly of 193 member states that partnerships with the private sector are "absolutely vital" and all must have access to drugs and vaccines to deal with this particular outbreak which means that virus samples and data must be shared and it was essential for drug makers to work with governments to avert the worst potential impacts of the new H1N1 strain. Ban has urged governments to think beyond their borders in their response to the H1N1 strain.

Experts fear that a drug-resistant strain may mix with the new H1N1 swine flu strain to create a dangerous new strain.

The WHO has been considering the risks of halting production of the seasonal flu virus to facilitated the production capacity for a swine flu vaccine - the WHO forecasts that it should be possible to produce 4.9 billion doses of a swine flu vaccine in a year, but only if full-scale production was launched.

The United Nations health agency is apparently banking on an output of 94.3 million doses a week but WHO Director General Margaret Chan says that is a very optimistic maximum capacity and a best-case scenario - it seems two doses might be needed for immunity from swine flu to be guaranteed.

Dr Chan says most of the cases of swine flu in Japan were linked to schools and the pattern of progress of the virus there was "not unusual" and the transparency of the Japanese authorities was appreciated.

Dr Chan says that vaccine makers have shown a very serious commitment to help the international community prepare for a pandemic of flu, which, while seemingly mild so far, could become more severe as it circles the globe.

Swiss pharmaceutical group Novartis said it had received samples of the new A(H1N1) influenza virus and was now waiting for the go ahead from the WHO to begin the vaccine process which would take three to four weeks.

Seasonal flu is each year responsible for as many 500,000 deaths and causes severe illness in millions and whether an H1N1-only vaccine is currently needed raises questions because it's production could reduce the world's supply of seasonal flu vaccines.

U.S. Health and Human Services Secretary Kathleen Sebelius has suggested that pharmaceutical companies should ramp up their production of seasonal flu vaccine and then later switch to pandemic vaccine production if necessary because there is so much uncertainty about how the H1N1 virus will behave and how many people would need to be vaccinated.

According to the WHO, pharmaceutical companies plan to produce approximately 480 million doses of seasonal vaccine in 2009 - each one containing three separate vaccines against the three most common circulating flu strains - 430 million doses would be available by July 31st.

The U.S. Centers for Disease Control and Prevention (CDC) says the number of confirmed cases of the new flu and are 'the tip of the iceberg' and estimates suggest there were now 100,000 cases.

The CDC's Dr Anne Schuchat said she was worried the new strain may mix with seasonal flu strains, which are still circulating - H1N1 strain is now reportedly resistant to the most commonly used antiviral Tamiflu but the inhaled drug Relenza was still effective.

Dr Schuchat says there is the risk that the circulation of the new virus together with the seasonal strains, will allow a re-assortment event where two viruses meet and swap entire stretches of their genetic material - this is a particular feature of flu viruses and some pandemics have emerged because of such genetic mixing.

In update # 33 from the WHO on the influenza A(H1N1) situation, as of the 19th May, 40 countries have officially reported 9,830 human cases and there have been 79 deaths but in many of the fatal cases those affected had underlying conditions that put them at risk or had serious medical conditions.

Worst affected countries to date are Mexico with 3,734 cases including 74 deaths, the U.S. with 5,123 cases and 5 deaths, Canada with 496 cases and 1 death and Japan with 159 cases and no deaths.

Next are Spain 103, UK 102, Panama 59, France and Germany 14 each, Colombia 11, Costa Rica, New Zealand and Italy 9, Brazil 8, China and Israel 7, El Salvador 6, Belgium 5, Chile 4, Cuba 3, Guatemala, Republic of Korea, Netherlands and Sweden 3,Finland, Malaysia, Norway, Peru, Thailand and Turkey 2 each and Argentina, Australia , Austria, Denmark, Ecuador ,India, Ireland, Poland ,Portugal and Switzerland all have had 1 case each.