GENEVA: The World Health Organization (WHO) called on all countries to monitor closely outbreaks of deadly avian influenza in birds and poultry, and to report any human cases promptly, warning: 'We cannot afford to miss the early signals'. 'Just since November of last year, nearly 40 countries have reported fresh outbreaks of highly pathogenic avian influenza in poultry or wild birds. The rapidly expanding geographical distribution of these outbreaks and the number of virus strains currently co-circulating have put WHO on high alert,' Dr. Margaret Chan told the UN agency's executive board in Geneva. In China, there has been a 'sudden and steep increase' in human cases of H7N9 since December and the WHO has not been able to rule out limited human-to-human spread in two clusters of cases although no sustained spread has been detected thus far, she said. (Reporting by Stephanie Nebehay; Editing by Dominic Evans)