In this tutorial, we will show you how to create a simulation of a virus spreading using Adobe After Effects. This effect is useful for educational purposes to visualize how a virus can spread across the world. Follow these steps to achieve this effect.

**Step 1: Prepare Your Map**

1. Download a free image of a world map.
2. Open Adobe After Effects and create a new composition. Name it "Main Composition" and set it to full HD resolution.
3. Drag the world map image into your Main Composition.

**Step 2: Extract the Background**

1. Select the world map layer and use the **Keylight (1.2)** effect from the **Effects & Presets** panel to key out the white areas of the map.
2. Create a new solid layer with a dark color and place it below the world map layer to create the illusion of a dark atmosphere.
3. Turn on the transparency grid to ensure the keyed-out areas are transparent.

**Step 3: Create the Fractal Spread**

1. Create a new composition and name it "Fractal Spread".
2. In the Fractal Spread composition, create a new solid layer. This layer will represent the spread of the virus.
3. Apply the **Fractal Noise** effect to the solid layer from the **Effects & Presets** panel.
4. Adjust the settings of the Fractal Noise effect to add complexity to your simulation. Increase the contrast and play with the brightness to achieve the desired look.

**Step 4: Animate the Spread**

1. In the Fractal Noise settings, animate the **Evolution** property to create the appearance of the virus spreading over time. Set keyframes at the beginning and end of your timeline with different Evolution values.
2. Adjust the **Scale** of the fractal noise to control the size of the spread pattern.

**Step 5: Composite the Spread onto the Map**

1. Return to your Main Composition and drag the Fractal Spread composition into it, placing it above the world map layer.
2. Set the blending mode of the Fractal Spread layer to **Multiply** or **Overlay** to blend it with the map.
3. Adjust the opacity of the Fractal Spread layer if necessary to achieve the desired effect.

**Step 6: Color and Final Adjustments**

1. Apply the **Colorama** effect to the Fractal Spread layer to change the color of the spread to represent the virus. Choose a color gradient that represents the intensity of the spread.
2. Fine-tune the color and opacity settings to make the spread effect more realistic and visually appealing.
3. Review your composition and make any final adjustments to the timing, position, or effects.

**Step 7: Render and Export**

1. Once you are satisfied with the final look, render and export your composition by going to **Composition** > **Add to Render Queue**.
2. Choose the appropriate settings for your final output and click **Render**.

By following these steps, you can create a realistic simulation of a virus spreading across a map using Adobe After Effects. For a detailed, step-by-step guide, watch the full video tutorial.