"On Dec. 29, The Gateway Pundit, a far-right website that often spreads conspiracy theories, published an article falsely implying that the Centers for Disease Control and Prevention had withdrawn authorization of all P.C.R. tests for detecting Covid-19. The article collected 22,000 likes, comments and shares on Facebook and Twitter. On TikTok and Instagram, videos of at-home Covid-19 tests displaying positive results after being soaked in drinking water and juice have gone viral in recent weeks... One TikTok video showing a home test that came out positive after being placed under running water was shared at least 140,000 times... Misinformation about Covid-19 tests has spiked across social media in recent weeks... The burst of misinformation threatens to further stymie public efforts to keep the health crisis under control."