While trying to avoid alarmism, global health agencies are steadily ratcheting up concern about bird flu in Asia. Bird viruses that can infect humans — particularly those of the H7N9 strain — continue to spread to new cities there.

Since October 2016, China has seen a “fifth wave” of H7N9 infections. Nearly 1,600 people have tested positive, almost 40 percent of whom have died.

Most had been exposed to live poultry, but a small number of clusters suggest that the virus could be passing from person to person. Continue reading.