The UK has more than 30million doses of drugs at the ready to combat a serious outbreak of swine flu, as health officials say they are prepared for the worst.
Anti-viral drugs will be a major weapon in the armoury of health organisations if the number of swine flu cases continues to accelerate.
The UK has stockpiles of two anti-viral drugs in particular - Tamiflu and Relenza - both of which have been effective in treating the H1N1 strain of swine flu in other countries.
Anti-virals are medication designed and used specifically for fighting viral infections. They are typically used to treat influenza, reducing the length of symptoms and usually their severity.
If a flu pandemic were to start, anti-viral drugs would be the first line intervention.
If administered quickly to all patients with symptoms, they can reduce the duration of the disease and the risk of complications, the Department of Health (DoH) said.
Anti-virals are also commonly used to treat HIV and the herpes virus.
The first anti-virals were developed in the 1960s.
Modern anti-virals work by targeting and disabling viral proteins.
A spokeswoman for the DoH said there was currently a stockpile of anti-virals to treat around 50% of the population.
The stockpile consists of approximately 22 million doses of Tamiflu and around 10.5 million doses of Relenza.
A global surveillance network called the Neuraminidase Inhibitor Susceptibility Network (NISN) has been set up with the World Health Organisation to monitor the possible emergence of viral resistance to these drugs.
The NISN monitors the situation globally, with particular emphasis on countries in which the neuraminidase inhibitors are used most frequently.
