"At this time we believe it is still too early to say that the pandemic is over. We are monitoring the situation carefully," said Dr Keiji Fukuda, the WHO's special adviser on pandemic influenza.
Addressing a telephone press conference, Fukuda said high levels of pandemic activity or infections were still continuing in many different countries, including France, Switzerland, Russia and Kazakstan.
He said the pandemic activity had clearly peaked and was on the way down in North America and some parts of Europe, but the peaking had occurred "extraordinarily early".
It remained unknown whether a new wave of infections would occur in the later winter or early spring months, he said.
"The pandemic is really a global event. The WHO will continue to monitor the situation in all parts of the world," Fukuda said.
He added that the WHO would continue to provide all possible support to countries that were particularly vulnerable in the face of pandemic infections.