While it's challenging to definitively determine the "most effective" herbs for antiviral properties, based on available research and traditional use, the following five herbs have shown promise in their antiviral activity:

1. Echinacea (Echinacea spp.): Echinacea is known for its immune-stimulating properties and has been studied for its effectiveness against viral infections, particularly respiratory viruses.

2. Elderberry (Sambucus nigra): Elderberry has demonstrated antiviral properties against certain strains of the influenza virus and may help reduce the duration and severity of cold and flu symptoms.

3. Garlic (Allium sativum): Garlic exhibits broad-spectrum antimicrobial activity, including antiviral properties. It has shown inhibitory effects against various viruses, although more research is needed to understand its full potential.

4. Andrographis (Andrographis paniculata): Andrographis has been used traditionally for its immune-enhancing and antiviral properties. It has shown effectiveness against respiratory infections and may help reduce the severity and duration of symptoms.

5. Licorice root (Glycyrrhiza glabra): Licorice root contains compounds that have demonstrated antiviral activity against various viruses, including herpes simplex virus and influenza virus. It also has immune-modulating properties.

Remember that individual responses to herbs can vary, and the effectiveness of herbs for antiviral purposes may depend on the specific virus and the individual's overall health. It's essential to consult with a healthcare professional for personalized advice and guidance regarding the use of herbs for antiviral purposes