Swine influenza is a highly contagious acute respiratory pig disease, which is caused by one of several swine influenza A virus. Pigs can also become infected with avian and human seasonal influenza and sometimes can become infected with more than one virus type at a time, allowing the genes from these viruses to mix.
Although swine influenza viruses normally only infect pigs, they do sometimes cross the species barrier and cause disease in humans.
What are the implications of swine influenza for humans?
Outbreaks and sporadic human infection with swine influenza have been occasionally reported. Symptoms are similar to those of seasonal influenza, although severe pneumonia, resulting in death, is also possible.
Since the typical symptoms resemble those of seasonal influenza and other acute upper respiratory tract infections, most cases have been detected by chance through seasonal influenza surveillance and the true extent of this disease among humans is unknown.
Where have human cases occurred?
Since 2007, the WHO has been notified of swine influenza cases from the United States and Spain.
How do people become infected?
People usually get swine influenza from infected pigs, however, some human cases lack contact history with pigs or environments where pigs have been located. Human-to-human transmission has occurred in some instances but was limited to close contacts and closed groups of people.
Is it safe to eat pork meat and pork products?
Yes. Swine influenza has not been shown to be transmissible to people through eating properly handled and prepared pork or other products derived from pigs. The swine influenza virus is killed by cooking temperatures of 160°F/70°C, corresponding to the general guidance for the preparation of pork and other meat.
Which countries have been affected by outbreaks in pigs?
Swine influenza is not notifiable to international animal health authorities, which means that its international distribution in animals is not well known. The disease is considered endemic in the United States and outbreaks in pigs are also known to have occurred in North America, South America, Europe, Africa and in parts of eastern Asia including China and Japan.
What about the pandemic risk?
It is likely that most people, especially those who do not have regular contact with pigs, do not have immunity to swine influenza viruses that can prevent the virus infection. If a swine virus establishes efficient human-to human transmission, it can cause an influenza pandemic. The impact of a pandemic caused by such a virus is difficult to predict because it depends on the virulence of the virus, existing immunity among people, cross protection by antibodies acquired from seasonal influenza infection and host factors.
Is there a human vaccine to protect from swine influenza?
There are no vaccines that contain the swine influenza virus currently causing illness in humans. It is not known whether current human seasonal influenza vaccines can provide any protection. Influenza viruses change very quickly. It is important to develop a vaccine against the currently circulating virus strain for it to provide maximum protection to the vaccinated people. This is why WHO needs access to as many viruses as possible in order to select the most appropriate candidate vaccine virus.
What drugs are available for treatment?
Antiviral drugs for seasonal influenza effectively prevent and treat the illness. Most of the previously reported swine influenza cases recovered fully from the disease without requiring medical attention and without antiviral medicines.
Some influenza viruses develop resistance to the antiviral medicines but viruses obtained from the recent human cases with swine influenza in the United States were sensitive to oselatmivir and zanamivir, although resistant to amantadine and remantadine.
Information is insufficient to make recommendation on the use of the antivirals in prevention and treatment of swine influenza virus infection. Clinicians have to make decisions based on the clinical and epidemiological assessment and harms and benefit of the treatment to the patient.
For the ongoing outbreak of the swine influenza infection in the United States and Mexico, the national and the local authorities are recommending to use oseltamivir or zanamivir for treatment and prevention of the disease based on the virus's susceptibility profile.
Source: World Health Organisation