Covid-19 arrived in Cambodia a year ago, on Jan. 23, when a Chinese national flew in from Wuhan, the city where the illness was first detected, and soon fell sick with a fever. A P.C.R. test to detect the genetic material of SARS-CoV-2, the coronavirus that causes Covid-19, came back positive. With that news, the disease had officially pierced the borders of another nation.
For Cambodia, a developing country with a rudimentary health care system and multiple direct flights from Wuhan, the new disease seemed to present an especially high risk.
Dr. Jessica Manning, a public health researcher with the National Institute of Allergy and Infectious Diseases, who had been working in Cambodia for years, also saw an opportunity: helping the country join the global effort to watch for new diseases.