WHO: Some regions still battle intense flu activity

Jan 8, 2010 (CIDRAP News) – Though pandemic flu activity continues to fall across much of the Northern Hemisphere, some parts of the world are hot spots for the virus, including parts of Europe, North Africa, and South Asia, the World Health Organization (WHO) reported today.

In its weekly global surveillance update, the WHO said countries in central, eastern, and southeastern Europe, such as Poland, Serbia, Ukraine, and Georgia, are reporting intense virus circulation. Increased activity in North Africa is particularly evident in Egypt.

Pandemic flu activity is still widespread with rates of respiratory diseases increasing in parts of South Asia, including northern India, Nepal, and Sri Lanka, the WHO reported.

Though the pandemic H1N1 strain is still dominant, small numbers of seasonal H3N2 viruses are circulating in northern China. In a virologic surveillance report accompanying today's update, the WHO said about 10% of influenza A viruses that have been detected in China are seasonal H1N1 and H3N2 subtypes. Sporadic detections of those two seasonal flu viruses, as well as influenza B, have also come from a few other countries, including Canada, the United States, and some European countries, the WHO said. (Today's weekly US update, however, said no seasonal H1N1 or H3N2 viruses were identified last week.)

Today's weekly report from the European Centre for Disease Prevention and Control (ECDC) said that over the last several weeks, 99.7% of influenza viruses were characterized as pandemic H1N1, with only four (less than 1%) H3N2 viruses, all of which were the Brisbane strain covered by North America's seasonal flu vaccine.

Among viruses submitted to the Global Influenza Surveillance Network, 190 cases of oseltamivir resistance have been identified so far, the WHO reported. All have shown susceptibility to zanamivir, the other neuraminidase inhibitor recommended to treat pandemic H1N1 infections. All of the viruses so far closely match the novel H1N1 virus contained in the vaccine.

Temperate regions of the Southern Hemisphere are seeing only sporadic cases of pandemic influenza with no sign of sustained community transmission, the WHO said, adding that the pattern suggests that population immunity levels in countries that had intense winter pandemic flu activity were high enough to block recurrence during summer when the virus is less transmissible.

Dr Angus Nicoll, head of the ECDC's influenza program, wrote in a Eurosurveillance editorial yesterday that as pandemic flu transmission decreases in many parts of the world, health authorities are looking ahead to plan their response to the next influenza season. He wrote that surveillance of severe acute respiratory illnesses, a striking feature of the pandemic virus, is needed to help officials tailor their recommendations for the next seasonal flu vaccine.

Though experts use the patterns of 20th century flu pandemics to gauge the next chapters of the current pandemic, influenza viruses are unpredictable, he said. For example, he pointed out that during the 2007-08 flu season the H1N1 virus quickly became resistant to oseltamivir (Tamiflu) without an apparent link to the drug's use.

Given the uncertainties, a prudent countermeasure is vaccination, Nicoll wrote. He noted that the European Union recently adopted seasonal flu vaccine recommendations that spell out member states' vaccination responsibilities. He said the ECDC will help address immunization issues, such as increasing coverage among older people (which varies widely among the states), documenting vaccine coverage in risk groups, and boosting immunization rates in healthcare workers.

Several European countries, as well as Australia, are discussing canceling or are negotiating to cancel some of their pandemic vaccine orders. Health officials in the countries say they anticipate large surpluses, as infections wane and demand for the vaccine ebbs. In some instances, countries placed their vaccine orders with the assumption that two doses would be needed to provide protection. However, clinical studies have shown that one dose is sufficient for all but the youngest age-groups.

See also:

Jan 8 WHO pandemic update 82

Jan 8 WHO weekly virologic surveillance update

Jan 8 ECDC influenza surveillance report

Jan 7 Eurosurveillance report

This week's top reads