Last year’s jump in avian influenza cases among Cambodians could be due to a mutation of the virus in Cambodia and southern Vietnam, experts said Tuesday at a meeting in Phnom Penh. They said it would be the first mutation here of the virus since it was first detected in the region a decade ago.
The new virus apparently mutated from two existing viruses. It was discovered around the time Cambodia reported its first human infections of 2013. Since January 2013, 35 Cambodians are known to have contracted the virus, a number that exceeded reports of any other country worldwide for that period.
“[W]hile the rest of Southeast Asia has had constant changes of the virus, it’s been very stable here—until the introduction of this new [virus subtype],” Dr. Dennis Carroll, the Washington-based director of USAID’s avian influenza unit, said at the meeting between international experts on bird flu and regional animal and human health officials from Vietnam and Cambodia.
“We got a novel first mutation that started around the same time in 2013 as we saw an increase of cases,” he said.
Previously, Cambodia typically saw about four or five cases per year. Last year, a total of 26 people, mostly children, were confirmed to have contracted the virus. Twelve died.
“So this is a significant increase, and we are not quite sure why this happened,” Dr. Carroll said.
Although the H5N1 virus primarily attacks poultry such as chickens and ducks, it can spread to humans who have close contact with dead or sick poultry. Health experts said that a virus mutation could allow it to heavily affect humans and enable it to spread much like a seasonal influenza.
The new variant that emerged in 2013, Dr. Carroll said, still mainly affected chickens. But it was also the dominant cause of last year’s infections in humans.
“[H5N1] has not—for all the mutations it’s gone through—it has never acquired the ability to efficiently affect people,” he said.
During the meeting, experts tried to determine why Cambodia saw a total of 26 cases in humans last year, while southern Vietnam only reported two.
“[The] elevated number of cases in Cambodia and the not corresponding cases in Vietnam raises some questions,” Dr. Carroll said.
The new mutation, greater prevalence of the virus, better reporting or a lack of preventive measures in Cambodia could be possible reasons.
“We have not a clue,” Dr. Carroll said. “We could fill a book with the number of questions that have come up in the last 16 months in this region.”
“Vietnam does take certain measures…Cambodia doesn’t take. They do promote vaccination, so that may be the reason why we don’t see the same level, but we just don’t really know,” Dr. Carroll said.
For Vietnamese officials, the matter was clearer. They said vaccination prevents the virus from freely circulating among chickens and ducks. Farmers there whose poultry has to be culled are compensated. This allows Vietnam to respond to bird outbreaks before human cases are reported, said Dr. Nguyen Ngoc Tien, an epidemiology specialist at the department of animal health at Vietnam’s Ministry of Agriculture.
“By [offering compensation] we have managed to encourage farmers to report the disease to the government and that’s why we have had a very rapid response to outbreaks,” he said. “They [farmers] don’t hide information and just throw the poultry away,” which would mean losing out on financial compensation.
In Cambodia, the Ministry of Agriculture has said that it has no plans to offer compensation, because poor farmers should simply report outbreaks out of a sense of public obligation.
In reality, most farmers eat their poultry when it falls ill, as they are too poor to afford losing their livestock.
Last month, Dr. Tien said, Vietnam also approved a $6.5 million budget to combat bird flu over the next five years.
The budget includes vaccination for poultry, which has been offered free of charge since 2005.
“Vaccination can help reduce the virus in poultry, meaning that the risk to human beings is also reduced. During 2004 and 2005, a lot of Vietnamese people were infected with the virus. But in recent years—last year we had only two cases—it’s only a few, and I believe that vaccination played a large role,” he said.
Since the introduction of vaccines for poultry, Vietnam vaccinated two billion birds.
Cambodia does not offer vaccination for H5N1.
Asked why Cambodia didn’t show the same commitment, Dr. Tien, the Vietnamese epidemiologist, said: “It costs a lot of money. In 2005, the [Vietnamese] prime minister decided that we want to protect human beings. We spent a lot of money, but we achieved this goal.”
Informal movement of poultry across the border is a concern. Because southern Vietnam and Cambodia share similar environmental conditions, a joint response was discussed during the two-day meeting.
Lotfi Allal, from the U.N.’s Food and Agriculture Organization in Cambodia, said that a pilot project across the Cambodia-Vietnam border would be set up in coming months to vaccinate poultry.