One of the most productive experiences editors at The Lancet have had during the past 6 months has been the intense collaborations with medical and public health scientists in mainland China and Hong Kong. Cooperation began early in the pandemic. During the last week of January, The Lancet published five research papers from mainland China and Hong Kong describing the clinical presentation of patients with COVID-19, human-to-human transmission, genomic relatedness to the SARS coronavirus, and the risks of a global pandemic. Those papers set out the story of the pandemic that has since evolved—from lockdowns to personal protective equipment, school closures to expanded use of intensive care services. The world owes Chinese and Hong Kong scientists a debt of gratitude for their carefully calibrated warnings. But today's global narrative is exactly opposite to that judgment. In the western world, China is seen as an increasing threat to international peace and security. Anti-China rhetoric reached its peak this week. The latest threat being promulgated is that, as one newspaper put it, “China will blitz the UK with a ‘cyber 9/11’”.The case against China has been widely articulated—the Chinese Government's “wolf-warrior diplomacy”; imprisonment and repression of the Uighur people in Xinjiang; denial of freedoms to Tibetans; belligerence towards Taiwan; the dangers of allowing Huawei to be part of western 5G technologies; and China's more assertive foreign policy. The latest concern has been the imposition of a national security law in Hong Kong. This new law is an ambiguous document. It insists that the “one country, two systems” policy is reaffirmed. The law pledges “a high degree of autonomy” for the Special Administrative Region. It promises the protection of free speech. But the law's intention is to prevent, suppress, and punish anyone engaging in activities that promote secession, subversion, terrorism, and collusion with a foreign country or external elements that endanger national security—with penalties that include life imprisonment. The law commits to strengthening supervision and regulation of universities, civil society, the media, and the internet. New institutions, such as the Committee for Safeguarding National Security, will report to Beijing, not to the authorities in Hong Kong. Mainland China can exercise jurisdiction over cases and decide where a trial can be heard. The first arrests took place on July 1, including a young man carrying a Hong Kong independence flag. Medical scientists in Hong Kong have described the law as “bitter medicine”. They worry it will diminish the attractiveness of Hong Kong for international research collaborations. They fear it will drive students out of Hong Kong. They think it might have a chilling effect on their freedom of inquiry. Whether these anxieties come to pass will depend on how the mainland government chooses to interpret the law. Tobias Ellwood, who chairs the UK's House of Commons Defence Select Committee, last week accused the Chinese Government of attempting to conceal the COVID-19 pandemic. He alleged “negligence in a Wuhan laboratory”. “The time to stand up to China is now”, he wrote, “and the country to do it is Britain”.The global emergency of COVID-19 is sharpening the confrontation between China and the west, exacerbated by President Trump's insistence on referring to the “China virus”. What should be the approach of western medical science to China? Some have argued for quiet engagement. Others suggest that engagement is nothing less than appeasement. At moments of geopolitical stress, it is surely better to avoid stoking tensions. It is surely better to intensify, not weaken, personal and institutional relationships. It is surely better to build more nuanced understanding between peoples. The present wave of anti-China sentiment has now evolved into a Sinophobia that threatens international health. China's 1·4 billion people are not immune to the economic shocks that are currently enveloping the world. A pandemic is a moment for solidarity between peoples, not conflict between governments. Instead of accelerating a new Cold War between the west and China, medicine and medical science can help to establish a new compact between nations. Rigorous questions can still be asked. Perceived encroachments on liberties can still be challenged. But these questions and challenges must be pursued through a commitment to strengthened cooperation, not hostile threats. A pandemic is a moment for conciliation, respect, and honesty between friends.