Diagnosing bird flu is difficult as its symptoms are similar to those of respiratory illnesses, Wadia said.
Only quick diagnosis and treatment can ensure effective medical treatment, he said.
"The latest deaths indicate that H5N1 is a particularly virulent pathogen, as we have seen in cases in other countries," Wadia said.
Globally, the human bird flu fatality rate is between 50 per cent and 60 per cent.
Wadia praised China for its efforts and its attitude in fighting the virus.
"The government has certainly not at all been complacent about this. They are remaining quite realistic," he said.
Indeed, the Health Ministry on Tuesday warned the nation about the dangers of complacency in terms of bird flu surveillance and monitoring of outbreaks.
"We cannot lower our guard in the slightest degree against the risk of bird flu triggering a new epidemic," the ministry's deputy director general, Mao Qun'an told a press briefing.
"As long as there are still outbreaks among animals... we cannot say bird flu is already past its peak."
In particular he warned against the nightmare scenario of bird flu starting to spread from human to human, rather than the current transmission pattern from bird to human.
Medical experts have warned human-to-human transmission could lead to a global pandemic that could kill millions of people.
The WHO cannot predict when a pandemic will occur, or if it will occur at all, Wadia said.
"As more outbreaks occur among poultry and animals around the world, and as more human cases occur, the virus has more chances to transmit more effectively from animals to humans, or possibly among humans as well," Wadia said.
The WHO has alerted countries, especially those in Asia, to be ready to respond quickly to any signs of emergence of a pandemic strain of the H5N1 virus.
Asia remains the centre of H5N1 avian influenza, as it is in this part of the world that the virus is prevalent, even entrenched, the spokesman said.
Bird flu has swept vast parts of Asia, killing at least 76 people in the region since 2003.