It was the highest number of human cases in the world and more than the total that Cambodia had recorded, since H5N1 was first detected there a decade ago.
So far this year, another four Cambodians have died from avian influenza.
This week, officials from Cambodia, Vietnam and international agencies have been meeting in Phnom Penh to try to work out why the numbers are higher and what to do about it.
Reporter: Robert Carmichael
Speakers: Dr Dennis Carroll, USAID; Lotfi Allal, FAO; market vendor Ly Mey
CARMICHAEL: Health experts say they don't understand why Cambodia last year recorded 14 deaths from H5N1, more than half the global total. Prior to that, Cambodia's worst year for human deaths from the virus was in 2011, when eight people died.
The reason for this surprise increase could be that the surveillance program reporting human cases of H5N1 is working well, picking up instances that otherwise would not have been detected.
Less positively, it could be that H5N1 is gaining more traction, or the increase could be due to something else entirely. At this stage, nobody knows.
What has the experts puzzled is that the H5N1 strain circulating in southeastern Cambodia is the same as that in southern Vietnam - yet Vietnam reported just four human infections since the beginning of last year.
Dr Dennis Carroll heads the pandemic influenza and other emerging threats unit at USAID, the US government's development arm.
CARROLL: "We're seeing a huge inequity between what's showing up on the Cambodia side versus what's showing up on the Vietnam side without any real obvious explanation."
CARMICHAEL: Dr Carroll hopes that this week's meeting will generate some insights.
CARROLL: "Ultimately the intent is to see whether or not we can do better cross-border coordination - identify gaps and knowledge and opportunities to coordinate some future activities towards getting a better understanding and hopefully coordinating better responses to this particular virus."
CARMICHAEL: H5N1 is one of many so-called zoonotic diseases - the name given to infections that originate in animals and that can pass to humans. Influenza-type illnesses are particularly problematic because they can mutate to allow easy human-to-human transmission.
The seasonal flu virus is one example of an influenza infection that transmits readily between people. But seasonal flu has a low fatality rate.
H5N1, on the other hand, has killed around 60 percent of the 650 people it has been shown to have infected globally over the past decade. To date, almost all H5N1 cases in humans have passed only from birds to humans. But the concern is that the virus could mutate to allow easy human-to-human transmission. The reason for the effort to tackle H5N1 is to make sure that never happens.
The source of avian flu is, of course, birds. And Phnom Penh's Chhbar Ampov market has plenty of poultry.
Cambodia is a predominantly rural country, and most of its 20 million chickens and ducks can be found in small clusters of four or five birds in village home backyards.
Controlling outbreaks in poultry, then, relies on villagers reporting when their birds fall ill. However the government won't compensate for poultry losses. Whatever the rights and wrongs of that - and compensation is a tricky topic - the result is that impoverished villagers would rather sell or eat sick and dying poultry.
Lotfi Allal is with the UN's Food and Agriculture Organisation, which works with the government on the animal side of H5N1. Although the main challenge is the lack of reporting of sick or dead poultry, he says, there are other difficulties too, including the unregulated cross-border trade between Cambodia and Vietnam.
LOTFI ALLAL: There are challenges of the informal trade in general in the country but [also] informal trade with neighbouring countries, which is a very huge challenge. This is linked with poultry but also linked with any other animals, adding a risk to the different challenges we are facing in the country.
CARMICHAEL: Birds that are sold typically end up in markets like Chhbar Ampov, where traders like Ly Mey slaughter them and sell them on. Conditions are far from hygienic, and government inspectors regularly find signs of H5N1 in markets like this.
LY MEY: (ACTUALITY)
CARMICHAEL: But Ly Mey isn't worried. She believes - wrongly, it should be said - that she can tell just by looking at a chicken whether it has avian influenza. She is also under the mistaken impression that only poultry from commercial growers can contract the disease.
CARMICHAEL: Clearly the experts have their work cut out for them. Although elements of Cambodia's approach to avian influenza have improved significantly in recent years, the experts know more needs to be done.