Q&A: Swine flu

Swine flu causes regular outbreaks in pigs

Infection control experts are looking into reports of deaths from an outbreak of swine flu in Mexico.

What is swine flu?

Swine flu is a respiratory disease which infects pigs.

Caused by influenza type A, there are regular outbreaks among herds of pigs, where the disease causes high levels of illness but is rarely fatal.

It tends to spread in autumn and winter but can circulate all year round.

There are many different types of swine flu and like human flu, the infection is constantly changing.

Can humans catch swine flu?

Swine flu does not normally infect humans, although sporadic cases do occur usually in people who have had close contact with pigs.

There have also been rare documented cases of humans passing the infection to other humans.

Human to human transmission of swine flu thought to spread in the same way as seasonal flu - through coughing and sneezing.

Is this a new type of swine flu?

The World Health Organization has confirmed at least some of the cases are a never-before-seen strain of H1N1.

It is genetically different from the fully human H1N1 seasonal influenza virus that has been circulating globally for the past few years and contains DNA that is typical to avian, swine and human viruses, including elements from European and Asian swine viruses

How many cases are there in the latest outbreak?

The Mexican government has confirmed 16 deaths from a swine flu outbreak and they are investigating 50 further possible deaths

The US Center for Disease Control and Prevention is also investigating seven non-fatal cases of human transmission of swine flu that have been reported since March 2009 but there has been no confirmation of a link.

How worried should people be?

When any new strain of flu emerges that acquires the ability to pass from person to person, it is monitored very closely in case it has the potential to spark a pandemic.

The World Health Organization is concerned but says it is too soon to change the threat level warning for a pandemic.