Dr. Luch berated herself for not remembering to test the boy a day earlier, when she might have saved him if she had treated him for the flu.
But the alarm she raised and the urgent activity that followed were testament to the strength of Cambodia's disease monitoring system and its importance to the global biosurveillance system.
It is the fruit of years of international and local investments, training and public education. It shows how frontline work in low-income countries is becoming increasingly important to a global system for detecting zoonotic diseases – pathogens that jump between animals and humans, as Covid-19 did. The goal is to identify and contain them, buy time to produce enough vaccines or drugs to treat them, or embark on a frantic mission to develop something new.
A growing threat
H5N1 is one of many viruses that cause flu in birds. It appeared in Hong Kong in 1996 and has since evolved into versions that have caused outbreaks in wild and farmed birds and occasionally jumped to humans.
In 2020, a new, especially fatal disease attracted the attention of scientists as it spread along migration routes to parts of Africa, Asia and Europe.
By 2022 it had reached North and South America and it was killing wild and domestic animals, including livestock and marine mammals.
So scientists were alarmed when Cambodia reported two people infected with H5N1 in February 2023. Was this the new version of the virus that returned to Asia and killed people? Such human cases had not occurred in the country for almost a decade, although scientists had discovered that the virus had also been present in birds all these years.
Genetic analysis has shown that the virus that infected the Cambodians was the known subtype, and not the one from America – a relief. Yet Cambodia has reported 11 people infected with bird flu in the past year, and five of them have died, more than anywhere else in the world.
Global concern about H5N1 has increased in recent weeks, since the virus was discovered in goats and dairy cows in the United States, and then in a Texas farm worker who fell ill.
As the virus moves between species, scientists fear that the virus could evolve and spread easily not only from birds to mammals, but also from person to person.