WHO | Pandemic (H1N1) 2009 briefing note 4

The number of human cases of pandemic (H1N1) 2009 is still increasing substantially in many countries, even in countries that have already been affected for some time.

Our understanding of the disease continues to evolve as new countries become affected, as community-level spread extends in already affected countries, and as information is shared globally. Many countries with widespread community transmission have moved to testing only samples of ill persons and have shifted surveillance efforts to monitoring and reporting of trends.

This shift has been recommended by WHO, because as the pandemic progresses, monitoring trends in disease activity can be done better by following trends in illness cases rather than trying to test all ill persons, which can severely stress national resources. It remains a top priority to determine which groups of people are at highest risk of serious disease so steps to best to protect them can be taken.

In addition to surveillance information, WHO is relying on the results of special research and clinical studies and other data provided by countries directly through frequent expert teleconferences on clinical, virological and epidemiological aspects of the pandemic, to gain a global overview of the evolving situation.

WHO | Pandemic (H1N1) 2009 briefing note 4