Planet Earth—a mere speck in our universe—is home to more viruses than there are stars in the cosmos. They exist at life's outer limit, performing a delicate dance that has lasted eons but can turn in an instant. Not alive, yet entwined with the living, viruses continue to challenge and surprise us.
Like when the news broke in March 2024 that bird flu had spread to dairy cows . "It was hard to believe," said evolutionary biologist Yvonne Su, who is an associate professor with Duke-NUS' Emerging Infectious Diseases Programme. Traditionally, cows had been thought not to be susceptible to bird flu or influenza A, the type of influenza that circulates freely in wild water and shorebirds.
Initially startled, her immediate next thought had been, "Is there direct cow-to-cow transmission?" When we spoke in early June, Su talked me through what little data was available at that time. While the number of unanswered questions rivaled the number of herds infected, some things were beginning to emerge. "We know it binds to the mammary glands in cows and we can see some cow-to-cow transmission," said Su.
By the end of the month, the genetic tree tracing the virus' evolution revealed an explosive epidemic. Virologist Gavin Smith, who leads Duke-NUS' Emerging Infectious Diseases Programme, summed up what he saw: "Everything is very closely related to each other. If you look at the distribution, it comes from a background where this virus is very widespread in wild birds and the environme.