An outbreak of swine flu in humans has health experts and officials around the world on high alert and there is great concern, as more countries report new cases of the disease, that the world may be on the brink of a pandemic.
Cases have now been confirmed in Canada, New Zealand, Spain and Mexico - where the outbreak appears to have started and while the World Health Organisation (WHO) is not recommending any travel or trade restrictions, last Saturday - the 25th of April, on the advice of the Emergency Committee, the Director-General, Dr. Margaret Chan, declared the situation a Public Health Emergency of International Concern.
Dr. Chan has called the outbreak a public health emergency of "pandemic potential" because the virus can pass from human to human.
According to the WHO, as of yesterday, there have been 20 confirmed human cases of swine influenza A/H1N1 in the United States, 18 in Mexico and another suspected 19 cases; the same strain is a suspect in the deaths of 86 people in Mexico.
The cases in the U.S. have occurred in New York, California, Texas, Kansas and Ohio and all have reported a mild flu-like illness and one person needed hospitalization.
To date no deaths have been reported in the U.S. and experts say in all 20 cases the viruses had the same genetic pattern and is being described as a new subtype of A/H1N1 never previously detected in swine or humans.
The WHO and the Global Alert and Response Network (GOARN) are sending experts to Mexico to work along with health authorities to determine exactly how the virus has spread and they are also investigating reports of suspect cases in other member states as they occur.
Some countries are taking the situation very seriously and warning against travel to Mexico and North America, planning quarantines and tightening the rules on pork imports and testing airline passengers for fevers; many of the cases had links to people who had traveled to Mexico, and all are the same swine flu strain.
WHO's emergency committee is meeting again on Tuesday 28th of April to examine the extent to which the virus has spread before deciding whether to increase the alert for a possible pandemic - this could entail issuing specific recommendations to countries on how to halt the spread of the disease - so far, WHO has only urged governments to step up their surveillance of suspicious outbreaks.
With suspected cases also arising in Israel and France, many countries are already taking precautionary steps by screening passengers from affected areas and quarantining anyone suspected to have the virus until the cause of the fever is determined.
Symptoms of the flu-like illness include a fever of more than 100 degrees Fahrenheit (37.8 degrees Celsius), body aches, coughing, a sore throat, respiratory congestion and, in some cases, vomiting and diarrhea.
Though the virus is usually contracted through direct contact with pigs, experts at the UN's animal health service say all the indications suggest that the virus is being spread through human-to-human transmission.
There is currently no vaccine available which specifically protects against swine flu and how much protection current human flu vaccines might offer remains unclear - it could be months before a vaccine is developed to protect against the new virus.
The U.S. Centers for Disease Control and Prevention (CDC) says there is concern that some people could die in the United States as the virus spread - stockpiles of the anti-flu drugs Relenza and Tamiflu are expected to be released to deal with the outbreak and local authorities have been told to plan for possible school closures to reduce the possibility of transmission.
The CDC is preparing a "yellow card" for travelers explaining the flu symptoms and what precautions to take and health officials are stressing frequent hand washing as the first line of defence against the virus.