How Flu Antivirals Work

Antivirals are medications used to prevent and treat infections caused by viruses. Flu antivirals work against the flu, which is caused by influenza A and influenza B viruses. Antivirals taken within 48 hours of flu symptoms can reduce the risk of flu complications, reduce symptoms, and shorten the length of the flu. Some antiviral medications can shorten the duration of flu symptoms by about 1 to 2 days, depending on the medication used. Antiviral medications can be used by most people (as recommended by their doctor), and they are recommended for people at risk for flu complications.

Antivirals, as the name implies, work against viruses. But how exactly? A viral infection occurs when the virus infects your body's cells, uses the cell to reproduce itself, and then leaves the cell to infect more cells in the body, which increases the amount of virus in the body.

Antivirals work by reducing the ability of the virus to reproduce.

Two classes of antivirals are used for the flu in Canada. One, called the M2 ion channel inhibitors, works by stopping the virus from entering the cell to infect it. This class of medications is effective against influenza A but not influenza B.

The antivirals used most often to treat the flu belong to the class of medications called neuraminidase inhibitors. These medications work against the influenza A and influenza B viruses by:

1. Interfering with the release of virus from infected cells.
2. Causing the aggregation of virus.
3. Perhaps helping the respiratory (lung and airway) secretions make the virus inactive.

In order for a flu virus to spread and infect other cells, it needs proteins on its surface to help it escape the current cell it's in and enter (infect) other cells where it can multiply further. These proteins on the flu virus's surface are enzymes called neuraminidases. The neuraminidase inhibitor antivirals work by blocking this enzyme on the viral cell's surface, which prevents the virus from being released from the infected cell. The antivirals block the enzyme by filling a small pocket.

When the reproduced virus is not able to infect other cells, the amount of virus in the body lessens, and you may feel less sick because your body doesn't have to work as hard to fight the virus.

For more information about treating the flu and reducing symptoms, read Flu home treatment and self care.