When a child in a small Cambodian town fell sick recently, his rapid decline set off a global disease surveillance system.
As Dr Sreyleak Luch drove to work the morning of February 8, through busy sunbaked streets in Cambodia’s Mekong river delta, she played the overnight voice messages from her team. The condition of a 9-year-old boy she had been caring for had deteriorated sharply, and he had been intubated, one doctor reported. What, she wondered, could make the child so sick, so fast?
“And then I just thought: H5N1,” she recalled. “It could be bird flu.”
When she arrived at the airy yellow children’s ward at the provincial hospital in Kratie, she immediately asked the child’s father if the family had had contact with any sick or dead poultry. He admitted that their rooster had been found dead a few days before and that the family had eaten it.
Luch told her colleagues her theory. Their responses ranged from dubious to incredulous: A human case of bird flu had never been reported in their part of eastern Cambodia. They warned her that if she set off the bird flu warning system, senior government officials might get involved. She risked looking foolish, or worse.
Anxious but increasingly certain, Luch phoned the local public health department, just across the street. Within minutes, a team arrived to collect a sample from the child, Virun Roeurn, for testing in a lab.
By then, Virun’s distraught parents had lost faith in the hospital. They demanded that he be sent by ambulance to the capital, Phnom Penh. His flu swab sample travelled with him.
Virun died on the journey. At 8pm, Cambodia’s National Public Health Laboratory confirmed Luch’s suspicion: He had died of highly pathogenic bird flu.
Luch berated herself for not having thought to test the boy a day earlier, when she might have saved him if she had treated him for influenza.
But the alarm she raised and the urgent activity that followed was a testament to the strength of Cambodia’s disease tracking system and to its importance to the global biosurveillance system.
It is the fruit of years of international and local investment, training and public education. It shows how front-line work in low-income countries is increasingly vital to a global system to detect zoonotic diseases — viruses that jump between animals and humans, the way Covid-19 did. The goal is to identify and contain them, buying time to produce enough vaccines or drugs to treat them, or to embark on a frantic mission to develop something new.
A growing threat
H5N1 is one of many viruses that cause influenza in birds. It emerged in Hong Kong in 1996 and has since evolved into versions that have caused outbreaks in wild and farmed birds and have occasionally jumped to humans.
In 2020, a new, especially deadly one caught the attention of scientists as it spread along migratory routes to parts of Africa, Asia and Europe.
By 2022, it had reached North America and South America and was killing wild and domestic animals, including livestock and marine mammals.
So, scientists were alarmed when, in February 2023, Cambodia reported that two people had been infected with H5N1. Was this the new version of the virus, returned to Asia and killing people? There had been no human cases in the country for nearly a decade, although scientists had found that the virus had been present in birds all that time.
Genetic analysis established that the virus infecting Cambodians was the familiar subtype, not the one in the Americas — a relief.
Still, in the past year, Cambodia has reported 11 people infected with bird flu, and five of them have died, more than anywhere in the world.
Global anxiety about H5N1 has risen higher in recent weeks, since the virus was detected in goats and dairy cows in the United States, and then in a Texas farmworker who fell ill.
As the virus moves between species, scientists fear the potential of the virus to evolve to spread easily not just from birds to mammals, but also from person to person.
And so the death of Virun, in a provincial Cambodian town, jolted the global system to attention.
At first light the day after Virun died, a team from the health department in Kratie arrived at the wooden house on stilts where he had lived. They swabbed everyone in the household and in neighbouring homes to test for flu and then went on to Virun’s school to test his classmates. At the hospital, and in other medical facilities around Kratie, any patient with a fever was screened.
A team from the Ministry of Agriculture, Fisheries and Forests rounded up the family’s half-dozen surviving chickens and those of their neighbours and took the birds away to be killed and burned.
The team went door to door through the community, asking everyone about illness in their chickens and ducks. Workers from the Ministry of Environment checked rice paddies and forested areas, looking for die-offs in wild birds; they did not find any.
In Phnom Penh, the national laboratory sent Virun’s sample down the road to the Institut Pasteur, the Cambodian outpost of a global network of public health research centres that date from the French colonial era. There, virologists confirmed the H5N1 diagnosis and compared the sample with a decade’s worth of influenza samples in the institute’s biobank. They confirmed that it was the familiar subtype of the virus.
Twenty-four hours after Virun died, the Pasteur lab uploaded genomic sequencing of the virus that had killed him to databases accessible to scientists worldwide. It notified the World Health Organisation, which sent out a global alert about a fatal human H5N1 case.
Back in Kratie, there was a new concern: Contact tracing had located another case, Virun’s older brother, Virak, 16. He had few symptoms but spent four days in isolation in the hospital, treated with Tamiflu, until he tested negative.
With the genetic sequences in hand, and after more gentle conversations with Virun’s shattered family, the disease detectives felt confident that Virak had been infected by the same dead rooster as Virun — and not by Virun himself. That meant Virun’s death was a chance misfortune, not the beginning of a global catastrophe of sustained human-to-human transmission.
‘Text me’
The effectiveness of Cambodia’s surveillance system can be credited in part to one man, Dr Ly Sovann, an apparently unsleeping tropical medicine specialist who runs the Cambodian Center for Disease Control.
“I have two phones, four SIM cards, so I never lose the network anywhere in the country, and people can always reach me,” Sovann said, brandishing a cellphone in each hand to demonstrate. He added: “You see something, you see an unusual respiratory disease, you see a cluster of diarrhoea cases — you text me. Because one, two hours, one day, it can make a big difference.”
His intensity stems from tragedy. Twenty-five years ago, when he was a young public health official, Sovann responded to a rural cholera outbreak. Dozens of people had died before the national health ministry even heard about it. When he took charge of the agency, he abolished the slow bureaucratic system that required provincial-level authorization to send samples to the capital for testing.
He created a national hotline that villagers can call toll free to report a sick or dead animal. He told private clinics and hospitals that the national lab would test their suspicious samples for free. His office issues a news release within hours of a confirmed case of human H5N1 or any other infectious threat.
His openness discomfits some in the hierarchy, his colleagues acknowledge privately. Bird flu reporting, for example, can hurt the livestock industry — poultry prices crash each time there is a human case.
Sovann brushes off the concern.
“Do you imagine that if Cambodia has many, do you think neighbouring countries don’t have a case?” he said. “I say, no. Now if we can detect, it means we’re good. It means our surveillance system is working.”
But the climate for free exchange of information in Cambodia is deteriorating. The increasingly autocratic government has shuttered independent news organisations. For now, Sovann still operates with a degree of independence. International organisations supporting disease surveillance here walk a delicate diplomatic line, seeking to keep the information channels open.
Protecting the international network is critical. The joint effort grew out of a deadly bird flu outbreak that began in Hong Kong in 2002 and started infecting people in the Mekong Delta two years later, killing 54 of the 100 people known to have contracted it.
The US Centers for Disease Control and Prevention was among the organisations that came to assist, training staff members and helping improve Cambodia’s public health laboratory so that samples would no longer have to be sent to France for analysis, which took a month to return a result.
The US Agency for International Development began, or USAID, to fund an expanded surveillance program, building on the idea that human, animal and environmental health experts needed to work together.
In exchange, the United States got access to virus samples that allowed the CDC to track emerging viruses, which helped inform development of new vaccines and therapeutics.
USAID has invested US$30 million ($49 million) in Cambodia’s bird flu response since 2006, and the World Bank has added US$19.5 million ($32 million) from its new Pandemic Fund.
Hospitals in Cambodia are now required to send the national lab five samples a month from patients with febrile illnesses, and samples from anyone with a severe respiratory illness. The agriculture ministry has similar requirements for livestock.
The recent news from the United States of bird flu in dairy cows has alarmed the Cambodians.
“The lesson learned from the US is that we need to look more in these other animals and do more tests,” said Dr Tum Sothyra, director of the National Animal Health and Production Research Institute.
The ministry is expanding testing to animals that are likely to eat infected birds, such as ferrets and wild dogs, but he hopes it can find the funds to test cows as well.
People in villages will report a sick buffalo, cow or pig, he said. Those could be a family’s most important asset — and if people see a neighbour’s buffalo die, they worry about their own.
Poultry, however, is more difficult to surveil. Cambodians typically eat chickens or ducks only around the big national holidays, such as Khmer New Year in early April — but there are at least 50 million birds being raised in people’s yards.
Sothyra’s staff collects samples from birds at markets across the country but can do little to trace the source when they find one that is positive for H5N1. The birds have been sold by then, and in any case, they may have passed through a dozen middlemen who combine flocks on the journey from household to market.
WHO recommends culling all birds in a radius of 1 kilometre from anywhere a bird has been found to have H5N1, but Cambodia culls birds only at the households and the immediate neighbours of confirmed cases.
“Government recognises the economic impact on people would be enormous,” said Dr Makara Hak, animal health adviser with the United Nations’ Food and Agriculture Organisation office in Phnom Penh. “Sometimes, I feel that people don’t think about the potential loss of life.”
Sothyra said the Cambodian government’s position is that it cannot afford compensation for culled birds and that it does not wish to encourage people to spread disease to get a payout for their birds.
But the lack of compensation means people are reluctant to report sick chickens. And despite a national public education campaign, they often eat those they find dead.
“You ask people, ‘Why did you eat it?’” Hak said. “And they say, ‘If I don’t eat, I don’t live.’”
Sam Chuon, a 56-year-old nurse who ran a community health centre in Ampil, was among those who died. He ate a chicken he had found dead, even though posters warning against it hung in his clinic.
No mourners allowed
Chuon was diagnosed with H5N1 from a posthumous sample after he died in an ambulance on the way to the capital October 7. The next day, a 2-year-old girl who lived about 14km away died of the virus. The overlapping cases spooked public health officials. There seemed at first to be no connection between them, but an epidemiology field team eventually discovered a poultry trader had visited both villages a few days before the nurse and the child fell sick.
Tith Na, the girl’s grandmother, knew that dead chickens could be dangerous, and so when her family’s birds began to die, she cooked them but did not let her granddaughter, Yurin, 2, eat the meal. When the child fell ill a few days later, the clinic said she probably had dengue fever. When Yurin, a talkative toddler, was still limp and silent with fever five days later, the family scraped together the money to hire a car and a driver to take her to the national pediatric hospital in Phnom Penh, three hours away. Yurin died there the next day, a few hours before her infection with H5N1 had been confirmed.
Hours after the family took her body home, public health officials came for the rest of their birds. Police ensured that no one from the community attended her cremation or joined her family as they buried her in the rice paddy in front of their one-room house.
Across the country at Virun’s home in Kratie, his mother, Ut Siyeang, sits on folded legs, rocking and weeping for hours each day. She talks about her studious middle son, and how they were saving all their earnings from a vegetable cart to pay for his dream of going to medical school.
Virun’s grandmother Chout Yeng said she believes the government made up this story about a bird disease to cover up incompetence at the hospital. When public health field teams came around for follow-up testing, she would not talk to them; Virun’s father chased them off.
Sovann said he knew there was still considerable public education to be done about bird flu. But to keep the country and the world safe, he needs more front-line health care workers like Luch, who are brave enough to raise the alarm.
“You could just do the small thing, but you could save many lives,” he said. “You could delay the next pandemic.”
This article originally appeared in The New York Times.
Written by: Stephanie Nolen
Photographs by: Thomas Cristofoletti
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