The swine flu first detected in Mexico cannot be contained according to WHO.

The World Health Organization (WHO) has raised the level of influenza pandemic alert for the H1N1 swine flu first detected in Mexico to phase 4.

Alert level four out of a possible six means there has been verified human-to-human transmission able to cause community-level outbreaks and the likelihood of a pandemic has increased. Phase six is a full pandemic. However, WHO are keen to stress that a pandemic is not inevitable.

The Director-General of WHO, Dr Margaret Chan, said that as the virus is now widespread, “containment of the outbreak is not feasible”. Closing borders and restricting travel will have little effect on the spread of the virus. However, it is important that anybody feeling ill delays international travel and people returning from international travel with symptoms seek immediate medical advice.

The virus is being described as a new subtype of A/H1N1 which has not previously been detected in pigs or humans. The term swine flu is a slight misnomer given that this particular strain is in fact a mutated form of bird, human and pig flu. Pigs are considered to have been the mixing pot for several flu strains resulting in this H1N1 swine influenza.

The first reported cases of swine flu in humans were in Mexico, where the virus is resulting in some fatalities. Since the outbreak of this particular strain of influenza was identified on 13 April, there have been 152 probable deaths in Mexico, although only 20 have been confirmed as swine flu deaths.

The people who died in Mexico from swine flu are reported to have been aged between 20 and 50, which is characteristic of pandemics of the past. One reassuring factor is all cases outside of Mexico are mild and no deaths have been reported elsewhere. Also the number of people being hospitalised with swine flu in Mexico daily is falling.

Mexico is bracing itself for the ramifications of an epidemic of the virus in the country. Facemasks are being handed out, large public gatherings have been cancelled and citizens are being told to stay away from public places. Schools have also been closed nationwide until 6 May.

WHO and the Global Alert and Response Network (GOARN) are sending experts to Mexico to work with the health authorities and aid in the clinical investigation of the flu strain.

The fact that the virus can be transmitted human to human is a cause for concern for many countries. Cases of swine flu have already been confirmed in the US, Canada, Spain, Scotland, New Zealand, Israel and Russia, with suspected cases in other European countries and as far afield as Australia and South Korea.

There are fears that swine flu could replicate events of 1968, when an H3N2 strain of flu killed over one million people globally, or even the devastating events of 1918, when the Spanish influenza is said to have taken the lives of more than 50 million people worldwide.

Countries across the world are taking precautions to limit any possible contamination. Tourists returning from Mexico are being screened upon arrival at international airports. The UK has stated that it is well equipped to cope with a potential outbreak and currently has enough stores of antiviral medication to treat around half the population.

Good hygiene practice is being advised to help prevent catching swine flu. Regular hand washing is advised, along with covering the mouth when coughing or sneezing and using a tissue whenever possible and disposing of it correctly. WHO has stated that there is no risk from well-cooked pork and pork products.

People who believe they could have contracted the virus are being asked to phone their doctors, rather than going into the surgery to limit the number of people they come into contact with.

For further information about swine flu, visit: http://www.who.int/csr/disease/swineflu/en/index.html