Feb 28, 2008

Oseltamivir-Resistant Influenza A (H1N1) reported in Japan, and persists in 15 nations in Europe, the USA and Canada

Today the European CDC and the WHO updated their online information regarding high-level resistance to oseltamivir (“Tamiflu”) by human seasonal Influenza A (H1N1) virus isolates. The WHO table of global data includes 5/100 (5%) virus isolates in Japan showing this high-level resistance, in contrast to no resistance earlier this flu season when this phenomenon was first reported from Europe. Today’s updated WHO global database can be found at: www.who.int/csr/disease/influenza/h1n1_table/en/index.html

The significance of these emerging oseltamivir-resistant human seasonal influenza A (H1N1) viruses is emphasized in today’s update on the website of the European Centre for Disease Prevention and Control (ECDC): “These are the first human influenza viruses resistant to oseltamivir found transmitting in the community anywhere in the world (boldtype added). Similar viruses have been seen before but usually following treatment and those viruses have not been able to transmit and infect and have rapidly disappeared…There is no evidence that the appearance of these new viruses are related to use of oseltamivir which is currently thought not to be widely prescribed in most European countries.” For the full 28 February ECDC report go to: http://ecdc.europa.eu/Health_topics/influenza/antivirals.html

The WHO global database update February 28 noted that the USA reported 9% of 453 influenza A (H1N1) virus isolates, Canada 9% of 211 isolates, and Hong Kong SAR, China 9% of 116 isolates as resistant to oseltamivir.

Oseltamivir-resistant influenza A (H1N1) viruses have now been reported in 15 European nations. These include Ireland (10.3% of 29 virus isolates tested), Switzerland (13.3% of 30 isolates), the Netherlands (26% of 50 isolates), France (38.6% of 207 isolates), Norway (66.1% of 124 isolates) and ten other nations.

Italy has tested 66 isolates, Spain 52 isolates, New Zealand 88 isolates, the Republic of Korea 54 isolates, and the Philippines 37 isolates without finding any oseltamivir resistance.

The origin remains unknown of these unprecedented human influenza viruses that are transmissible from person-to-person despite being oseltamivir-resistant. Testing results of much larger numbers of human and animal influenza virus isolates from nations in Asia, the Americas, and Africa will be very important to help assess the epidemiology of these highly-resistant (H274Y mutation) viruses.

Expanded testing of animal influenza viruses for oseltamivir-resistance could help assess the hypothetical issue of animals having been exposed to oseltamivir, and subsequently contributing to the emergence of oseltamivir-resistant human influenza A (H1N1).

Daniel R. Lucey, MD, MPH

Director, Center for Biologic Counterterrorism & Emerging Diseases

EROne Institutes, Department of Emergency Medicine

Washington Hospital Center, Washington DC

Adjunct Professor of Microbiology and Immunology

Georgetown University Medical Center

Website for this posting: www.BePast.org

Email:DRL23@Georgetown.edu