A 7-year-old boy became the fourth person to die from the disease in Thailand. There have been nine fatalities in Vietnam.
An outbreak in China's poultry stocks, meanwhile, appeared to be widening with new confirmed or suspected cases reported in six provinces.
Also Tuesday, international experts were holding an urgent meeting in Rome at the U.N. Food and Agricultural Organization to discuss the bird flu, reports CBS News' Sabina Castelfranco. The experts hope to develop a coordinated strategy to respond to the emergency.
After announcing Monday that investigators could not trace the infections of two Vietnamese women to contact with chickens and that human-to-human transmission could not be ruled out, the WHO sought to calm fears that the case might foreshadow a global flu pandemic.
"We do not at this stage have a pandemic strain of influenza," said Mike Ryan, head of WHO's global epidemic response network. "We have a strain of influenza with the potential to pick up human genes and we're nowhere close to declaring a pandemic."
Neither a human nor a chicken source could be ruled out in the Vietnam case, but even if the women did catch the disease from a family member, limited human-to-human transmission of the virus is not the real danger.
What experts fear is the virus mutating into a form that passes easily between people — a pandemic strain that is a hybrid of the bird virus and a normal human influenza variety.
"What we really need to be able to do in this particular case is rapidly detect any (genetic) changes in the makeup of the virus," Ryan said. "We're not dealing with an imminent threat to public health, but we are dealing with a potential threat."
Indonesia acknowledged finding the same deadly H5N1 strain of bird flu that has jumped to humans elsewhere in Asia, but said no people in the country have been infected. Previously local officials said only milder versions of bird flu — ones not known to infect humans — had been confirmed.
Ten countries are battling bird flu and at least 45 million chickens have been slaughtered across the region to stop its spread. Nations that have seen their poultry industries ravaged by the epidemic continued to struggle with the economic fallout Tuesday.
Vietnam tour operators reported mass cancellations while Thai officials gave away cooked chicken and eggs to restore confidence in their billion dollar poultry industry.
Malaysia, which has not reported any bird flu cases, said it has stopped giving chicken meat to animals at the national zoo and is feeding them rat and rabbit instead.
FAO officials said they believe the disease is spreading within Thailand and Vietnam, but that the situation is less clear for China, where investigators may just now be picking up previously undetected cases.
Suspected cases in Chao'an county in China's southern Guangdong province were confirmed Tuesday. New suspected cases were reported in Gansu province in the west, Anhui in the east, Shaanxi in the north and the central provinces of Hunan and Hubei.
Governments battling the disease include China, Thailand, Vietnam, Cambodia, Laos, Indonesia, Japan, Pakistan, South Korea and Taiwan. However, health officials say the strain of bird flu striking Taiwan and Pakistan is milder and is not considered a serious threat to humans.
FAO announced it would give $1.6 million in emergency aid to Laos and Cambodia as well as Vietnam and Pakistan to help fight outbreaks in those countries.