During a pandemic, you really want the Centers for Disease Control and Prevention (CDC) to know their stuff. An organization that contains the absolute pinnacle of expertise on disease. What you don't want is an organization that, thanks to a typo, appears to think that cancer is the second biggest cause of cancer.
In a strange error, that's what the CDC claimed on Friday. The CDC likely meant to tweet that cancer is the second leading cause of death in the US, but that didn't stop people who are frustrated with messaging from the organization over the last few months and years from piling in to mock them.
This is precisely why it's best to check your tweets before you send them, especially if you're in charge of a nation's health.