Several countries, including Mexico and the United States, have reported outbreaks of swine flu, sparking fears of what some disease experts say could become a pandemic.
Here are some facts about swine flu:
What is swine flu?
The World Health organisation says swine influenza, or "swine flu" is a highly contagious acute respiratory disease typically found in pigs. It spreads through tiny particles in the air or by direct contact.
The virus tends to infect large numbers of a given pig population, killing between one and four per cent of those affected, the WHO says. Not every animal infected displays symptoms.
How do humans contract the virus?
Swine flu normally only infects pigs, but the virus can cross the species barrier and infect humans, the WHO says.
People can catch the virus through contact with infected pigs, though there have been limited instances of human-to-human transmission.
What are the symptoms of swine flu in humans?
Symptoms are similar to those of human strains of the seasonal influenza virus, including fever, cough sore throat and body aches.
But the symptoms can also include severe pneumonia that can result in death, the WHO says.
Where do outbreaks occur?
Swine flu is considered endemic in the United States, though outbreaks in pigs have also been reported elsewhere in North America, South America, Europe, Africa, and in parts of eastern Asia.
How high is the risk of a pandemic?
If the virus establishes efficient human-to-human transmission, it can cause a pandemic, the WHO says.
Health officials say the swine flu might develop into a form easily spread among humans by combining with a human flu virus or mutate on its own into a transmissible form.
But Dr Laurence Gerlis, an expert on infectious diseases, told Al Jazeera it is too early to call the outbreak a pandemic.
"If you have got an epidemic that affects several countries in the world then it becomes a pandemic.
"But at the moment it is a problem in Mexico and people who have travelled to Mexico have carried it elsewhere. We have to assess it on an hour-by-hour basis."
Is it safe to eat pork products?
Properly handled and prepared pork products are safe to eat, according to the WHO. The swine flu virus is killed when cooked at temperatures of 160 F/70 C or higher.
Does a vaccine exist?
There are no vaccines to protect humans from the current swine flu virus.
The flu virus evolves quickly, meaning that vaccines are soon obsolete.
Health officials say there is no evidence to suggest that the vaccine prepared for seasonal flu will protect against swine flu.
Are there any other treatments?
The swine flu virus detected in Mexico and the United States appears to respond to treatment with oseltamivir (Tamiflu) and zanamivir (Relenza).
What can be done to stop the spread of the disease?
Most of the cases have been detected by chance through seasonal influenza surveillance.
But Dr Gerlis told Al Jazeera that "anyone travelling out of Mexico could be potentially carrying the virus and would have no symptoms at all."
Health officials say maintaining good hygiene, including regular hand-washing and staying a safe distance from those infected, may help in preventing the spread of the virus.
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