Which means a) no need to panic, but definitely a good idea to keep an eye on things in case we do observe human<->human transmission and b) Maybe we need to revisit how we raise animals for food....
Maybe the problem isn't how, but how many.
> The discovery of two cases of bird flu within the same family in Cambodia has highlighted the concern over potential human-to-human spread of the virus, although experts have stressed the risk remains low.
The issue is that each mammal/human infection gives the virus the possibility to adapt to mammals/humans and/or reassortment with other influenza viruses, like happened with H1N1/09.
The headline is irresponsible and fear-mongering clickbait, even just by referencing the contents of the article below it.
> The discovery of two cases of bird flu within the same family in Cambodia has highlighted the concern over potential human-to-human spread of the virus, although experts have stressed the risk remains low.
By the third paragraph, you will know that human-to-human transmission hasn't even been confirmed in this case. By the fourth paragraph, you will know that the thing "worrying" the WHO is the growth of human cases, not this particular case.
Unfortunately, most people don't read past the headline, and the Guardian knows it.
The Guardian's headline is "WHO says avian flu cases in humans ‘worrying’ after girl’s death in Cambodia"
This sounds a) reasonable grounds for worry by someone who studies epidemics and b) an accurate headline by the Guardian.
What does this have to do with the accuracy of the headline? You're just appealing to authority -- but the same authority figure says, in the same article, that the 2 cases in Cambodia may not even be an example of human-to-human transmission:
> “So far, it is too early to know if it’s human-to-human transmission or exposure to the same environmental conditions,” Briand told a virtual press conference hosted in Geneva.
The line you're quoting also explicitly says that the "worry" is general spread, not this particular example.