Covid-19 will become a pandemic. We don’t yet know how severe it will be, nor do we know if the virus will spread to all continents, but it’s already spreading widely in China, South Korea, Italy, Iran and elsewhere – and thousands of undetected and infectious patients have been and continue to travel around the world. This is unprecedented. Other than influenza, no other respiratory virus has been tracked from emergence to continuous global spread. The last moderately severe influenza pandemics were in 1957 and 1968; each killed more than a million people around the world. Although we are far more prepared than in the past, we are also far more interconnected, and many more people today have chronic health problems that make viral infections particularly dangerous. Based on extensive planning for an influenza pandemic by many national and international experts, we must do eight things – some immediately and some in the coming months – as we shift from the initiation phase of the pandemic to the acceleration stage: The virus and appropriate interventions will behave differently in high-resource than in low-resource areas, depending on crowding, capacity for diagnosis and treatment, and ability to reduce spread. We don’t yet know if Covid-19 will result in thousands, hundreds of thousands, or millions of deaths. Above all, we must do no harm. We don’t shut schools every year for seasonal influenza, and we didn’t shut them for the 2009 H1N1 influenza pandemic, for good reason: The severity level didn’t merit it. If the virus did emerge from the wet market selling exotic animals for food in Wuhan, then China’s failure to close such markets after SARS is the fundamental cause of this outbreak. On the other hand, China’s extraordinary cordon of Hubei province and other areas bought the world at least a month of lead time to prepare. The past week’s news means that the world must take these steps, and fast, to limit the health, social and economic harms of the COVID-19 pandemic.