The World Health Organization has declared "Disease X" a possible and deadly disease that could harm humanity on a global scale. The disease has not yet appeared, and scientists are working to decipher the multiple virus species harbored in animals that have the potential to jump to humans, causing catastrophic consequences. Avian flu is one of these deadly viruses threatening humans. As the Earth's climate changes, disease-carrying insects migrate and threaten to spread more viruses. Scientists are continually working to monitor and address these risks that could harm humankind.