PHILADELPHIA — Fear of COVID-19 never ended for Heather Kerstetter. She rarely leaves her home near Temple University for anything other than doctors’ appointments. Spinal muscular atrophy puts the 33-year-old at grave risk from respiratory infections, and even a cold can send her in the hospital with pneumonia for weeks. COVID could kill her. Yet she maintains a thriving social life alongside a deep network of people facing similar circumstances. She is part of a sprawling, diverse online community known as #DisabilityTwitter that provides people with disabilities a forum for dialogue, advice…
