San Francisco, April 30 : Facebook has issued 40 million warning labels across its services related to fake content around COVID-19, Its CEO Mark Zuckerberg has informed. Facebook has partnered with independent fact checkers who have marked more than 4,000 pieces of content related to COVID as false. Zuckerberg said that warning labels work because 95 per cent of the time when someone sees a warning label, they don't click through to view that content. "We put COVID-19 Information Center at the top of everyone's Facebook app, and so far we've directed more than 2 billion people to it. Equally important is also limiting the spread of misinformation. We don't allow content that puts people at imminent risk of physical harm," the Facebook CEO said late Wednesday. When people share hoaxes like that inhaling water, curious COVID, which is both false and will be physically harmful if anyone does that, we take that down. "In many of the places that have been hardest hit by the virus, messaging volume has increased more than 50 per cent and voice and video calling has more than doubled across Messenger and WhatsApp," Zuckerberg informed. Facebook has announced that it is working to connect symptom surveys to ground truth infection rate data from large serology in PCR studies that are funded separately by the Chan Zuckerberg Initiative, "in order to more accurately determine the true infection and exposure levels globally on a local-region basis as well". "So that means that we can make sure that the data is meaningful. But we're very focused on doing this in ways that we know are going to be helpful to the health response and that protect people's privacy and human rights, which is why we've primarily focused on how aggregate data can help," Zuckerberg added. /IANS