Bill Lau and his sister Dora Wang live in a retirement community in California. Covid-19 infections have reached record highs in the United States, the country which now has the largest number of cases in the world. Even in the early stages of the pandemic, the coronavirus has been spreading in senior care homes. The news was alarming for Bill and Dora. Like many people around the world, they have had to restrict their usual daily activities and follow strict social-distancing measures. But the…