1.   Flu viruses originate in waterfowl and commonly move through several species, chiefly pigs, before infecting humans.

2.   The lack of evidence of infection on local farms has stoked suspicion that the virus originated in mainland China.

3.   The territory had banned imports of chickens, ducks and geese from China, although it said there was no evidence that the flu virus had originated there.

4.   There is no evidence of infection on local farms, which has stoked suspicion that the virus originated on the mainland.

5.   To find a cure for the dreaded malady, scientists must send a brave and resourceful volunteer back in time, to find where the virus originated.

6.   While many influenza viruses originate in people, some start in animals and then make the leap to people who have no natural resistance.

7.   Ebola virus baffles researchers because no one has discovered where the virus originated or whether an animal serves as its natural host.

8.   Hong Kong officials said they suspected the virus originated in south China farms.

9.   It has been a mystery all along why there have been no reports of bird flu cases from the mainland, though health experts believe the virus originated there.

10.   It has repeatedly denied that the virus originated in Guangdong despite unconfirmed media reports of poultry die-offs.