Weekly update on oseltamivir resistance to influenza A (H1N1) 2009 viruses (August 18 2010, edited): 2 additional drug resistant virus detected; 304 i

[Giuseppe]

Weekly update on oseltamivir resistance to influenza A (H1N1) 2009 viruses (August 18 2010, edited)


[Source: World Health Organization, full PDF Document (LINK). Edited.]

Weekly update on oseltamivir resistance to influenza A (H1N1) 2009 viruses

18 August 2010


For this reporting week (11 - 18 August 2010), 2 new cases of oseltamivir resistant pandemic influenza A (H1N1) 2009 viruses have been reported. It brings the cumulative total to 304(1) so far. All but one of these(2) have the H275Y substitution and are assumed to remain sensitive to zanamivir.


Weekly update on oseltamivir resistance to influenza A (H1N1) 2009 viruses

[WHO Region: AFRO - EMRO - EURO - PAHO - SEARO - WPRO]

• Number of oseltamivir resistant isolates - 1 - 1 - 99 - 83 - 0 - 120

Proportion of the clinical background of reported cases of oseltamivir resistance (as of 18 August 2010).

• 28%, Immunosuppressed patients (1)
• 33%, Associated with treatment (2)
• 6%, Associated with postexposure prophylaxis (3)
• 9%, No known association with drug use, including known or suspected cases of person to person transmission (4)
• 24%, Preliminary notification (5)

Cases are classified first by identifying those that occur in severely immunocompromised patients (1), the majority of which are associated with oseltamivir treatment. The remaining cases are then classified as either occurring during or after oseltamivir treatment (2), associated with post-exposure prophylaxis (3), or occurring in patients who had not used antiviral drugs prior to occurrence of the resistant virus (4). The balance of cases (5) are those where insufficient clinical information is available.


(1) The totals reported here are based on confirmed reports from several sources, and include case reports published in medical journals, as well as reports from national ministries, health agencies and laboratories.
(2) WHO Euro region report a case of pandemic A(H1N1) 2009 virus that developed in an immunocompromised child with reduced susceptibility to zanamivir and oseltamivir due to an aminoacid mutation at position 223 in the neuraminidase. The clinical implications of this A(H1N1) 2009 variant are being assessed and a publication is expected. The report is available at (EuroFlu).

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