When coronavirus claimed its first victim in India's largest slum in April, many feared the disease would turn its narrow, congested streets into a graveyard, with social distancing or contact tracing all but impossible. But three months on, Mumbai's Dharavi offers a rare glimmer of hope with new infections shrinking, thanks to an aggressive strategy that focused on "chasing the virus, instead of waiting for disaster", according to city official Kiran Dighavkar.