21.   But Murray urged doctors and veterinarians worldwide to review their records of respiratory disease to see if the virus has appeared before.

22.   But this particular virus appeared to be able to do so.

23.   Doctors say the virus appears to be relatively inefficient, as it is spreading only slowly.

24.   Experts say the virus appeared to be spreading mainly by direct contact with chickens but human-to-human transmission could not be ruled out.

25.   Ostroff said he was gratified that while the virus appears to be spreading among wild birds and insects, there has not been a rapid increase in human infections.

26.   So far, the virus appears to be spreading slowly.

27.   Spano said there are no plans now for aerial spraying, which was undertaken last year when the virus first appeared.

28.   So far this year the virus has appeared only in birds and mosquitoes - bloodsucking insects that can spread West Nile to humans.

29.   The deadly virus appears to be resting for the winter.

30.   The Ebola virus appeared in Zaire and killed scores before quarantine and other measures brought it under control.