Localized pandemic flu transmission is persisting in Tanzania and Rwanda. Several countries in the tropical zones of the Americas are reporting localized flu activity as well, including Cuba, Guatemala, Peru, and Bolivia. WHO said in its weekly flu report that the significance of the rise in pandemic flu in parts of Chile to the rest of its flu season is unknown.
Data from Mexico suggest that several states reported localized activity throughout March, particularly in Federal district, an area that has reported recent spikes in severe and fatal pandemic H1N1 infections, the WHO said. Brazil, which has reported increased levels of influenza-like illnesses over the past month, has reported that most of the severe and fatal pandemic H1N1 infections are occurring in the country's northern regions.
In some parts of the world, including China and European countries such as Italy, flu activity is occurring at expected levels, much of which is influenza B. Other countries reporting increased detections of influenza B strains include Hong Kong and Chinese Taipei. Some parts of Africa, such as Cameroon, are also reporting influenza B illnesses.
Small number of seasonal H3N2 viruses have been detected in West and East Africa, the WHO said. Indonesia is still the most active area for seasonal H3N2 transmission, though activity is leveling off there, the WHO said.
In addition, the seasonal H1N1 virus has been reported sporadically by the Russian Federation.
Most pandemic virus samples that countries have submitted to WHO collaborating center laboratories are closely related to the strain recommended for pandemic influenza vaccines.
Ten more cases of oseltamivir-resistant pandemic H1N1 were reported last week, most of which occurred in the last quarter of 2009, WHO said. All 278 samples so far have the H275Y substitution, and all remained sensitive to zanamivir. Most cases were linked to treatment or postexposure prophylaxis or occurred in severely immunocompromised patients. Only 7% had no known association to treatment.
In addition, WHO said it has received preliminary notification about a pandemic H1N1 isolate that has reduced sensitivity to neuraminidase inhibitors.
So far more than 213 countries and overseas territories or communities have reported lab-confirmed pandemic H1N1 cases, the WHO said. The agency has received reports of more than 17,700 deaths, a number it says greatly underestimates the true burden of the disease.