Bird flu has reappeared in eight Thai provinces, while Vietnam has confirmed another human case of the virus that has killed 20 people in Asia.
The new Thai cases were found among fighting cocks in eight provinces where mass culls had been carried out.
The BBC's Kylie Morris in Bangkok says it is a blow to the government, which had planned to declare the country free of bird flu by the end of this month.
Test have also confirmed that a leopard in a Thai zoo died from the virus.
There were conflicting reports on whether the leopard had died from the H5N1 virus - the same strain that has killed humans.
The animal died in Kaokiew Zoo, 60km (40 miles) east of Bangkok, on 27 January, after several days of respiratory problems. A tiger at the same zoo was reportedly recovering from the virus.
Over the weekend, a teenage boy became the sixth person to die from the virus in Thailand.
Vietnam infection
In Vietnam, the only other country where the virus has passed to humans, 14 people have died.
AVIAN FLU ALERT
On Monday, authorities in Vietnam confirmed that a 15-year-old boy in the north of the country had become the 21st person to be infected.
Our correspondent says Thailand had declared optimistically that it would have the virus under control by the end of the month despite warnings from agencies like the United Nations Food and Agriculture Organisation, that the epidemic could take several months to eliminate.
In addition to the new infections in eight provinces, the Thai agriculture ministry said the virus had spread to ducks in another province, where mass slaughter of poultry had not previously been carried out.
Tens of millions of chickens and ducks have already been slaughtered across Asia as the outbreak has also hit China, South Korea, Cambodia, Taiwan, Indonesia, Pakistan, Laos and Japan.
So far there is no proof that the virus can pass from human to human.
Health experts are worried that if the virus mixes with a regular human influenza strain, it might create a mutant form that was able to pass between humans, triggering a human flu pandemic.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©