All you must know about swine flu (AH1N1)

by S. C.

What is swine influenza?
Swine influenza (swine flu) is an acute viral infection of the respiratory tract in pigs, caused by type A influenza virus. The mortality rate is low in pigs and recovery usually occurs within 7–10 days. Swine-origin influenza viruses also occur in wild birds, poultry, horses and humans, but interspecies transmission is considered a rare event. So far three influenza type A virus subtypes have been found in pigs: H1N1, H1N2 and H3N2.

Can swine influenza infect humans?
Yes. Human infections with swine influenza have been detected occasionally since the late 1950s usually in persons with direct exposure to pigs (e.g. people working in pig farms, etc.). In Europe, since 1958 a total of 17 cases have been reported. In the US in 1976, an outbreak of swine influenza virus infections in humans was detected among recruits in a military camp in Fort Dix, New Jersey. A link to pigs was presumed but never established. Instead there was extensive human-to-human transmission, with over 200 infections resulting in 12 hospitalisations and one death.

What are the symptoms of swine influenza in humans?
Symptoms of swine influenza in humans are usually similar to regular human seasonal influenza symptoms, involving fever of sudden onset and respiratory symptoms; diarrhoea might also occur. However, severe complications could occur even in normally healthy persons who become infected with the virus.

How do humans become infected?
Most commonly, swine influenza is transmitted through direct contact or close proximity with pigs. Secondary cases following human-to-human transmission have been reported in the past but they have been very rare.

Can swine flu be transmitted to humans by eating pork and pork products?
No. The swine influenza virus is not transmitted by eating properly handled and cooked pork and pork products. The swine influenza virus is killed by cooking pork to an internal temperature of 160°F/70°C. To date, there is no epidemiological evidence to suggest that the virus could be transmitted through eating contaminated pork or pork

Is there a vaccine against swine influenza?
Yes, there is a vaccine available for pigs against swine influenza, but there is no vaccine to protect humans from swine influenza (but see Q7, below).

Is the seasonal influenza vaccine effective against swine influenza?
There are certain similarities between the H1N1 human influenza viruses (covered by the seasonal vaccine) and the new H1N1 swine influenza viruses so one can not rule out some cross-protection. However, investigations need to be undertaken to determine whether this is the case. Those investigations are under way, but will take quite some time.

Can swine influenza in humans be treated?
Most swine influenza viruses have been susceptible to antiviral medications such as neuraminidase inhibitors (oseltamivir and zanamivir) and older antiviral drugs (amantadanes). The virus that is now being detected is susceptible to neuraminidase inhibitors but resistant to amantadanes.

Why does the current situation present a new problem?
The novel influenza virus (human swine influenza A(H1N1)) that has now been found contains genes from pig, bird and human influenza viruses, in a combination that has never been observed before anywhere in the world. In addition there is every indication that this virus has been transmitting from human to human and the resulting illnesses have been severe in a substantial number of cases in Mexico.

Source: European Centre for Disease Prevention and Control