Drug-resistant Influenza A Virus Potentially Serious To High-risk Patients
http://www.sciencedaily.com/releases/2009/03/090302115749.htm
ScienceDaily (Mar. 2, 2009) — A mutation of the influenza A(H1N1) virus that is resistant to the
drug oseltamivir may pose a serious health threat to hospitalized patients who have a
weakened immune system, according to a new study.
A global emergence and rapid spread of oseltamivir-resistant influenza A(H1N1) viruses
carrying a neuraminidase (NA; an enzyme) gene H274Y mutation has been observed since
January 2008. Viruses carrying this mutation have been presumed to be of lower risk and less
likely to be transmitted. "However, current widespread circulation of oseltamivir-resistant
influenza A(H1N1) viruses associated with typical influenza illnesses and viral pneumonia
suggest that these viruses retain significant transmissibility and pathogenicity [ability to cause
disease]," the authors write.
Jairo Gooskens, M.D., of Leiden University Medical Center, Leiden, the Netherlands, and
colleagues analyzed the transmission of the oseltamivir-resistant influenza A(H1N1) virus with
NA gene H274Y mutation to two hematopoietic (the formation of blood or blood cells) stem cell
transplant recipients and an elderly patient in a Dutch university hospital in February 2008. The
investigation included a review of the medical records and various influenza and genetic tests.
The analysis confirmed that four patients in the hospital had the virus mutation, and that the
virus was most likely transmitted while these patients were in the hospital. Influenza virus
pneumonia (3 patients) and attributable death (2 patients) during active infection was observed
in patients with lymphocytopenia (having an abnormally low level of white blood cells, important
to the immune system) at onset.
Five health care workers developed influenza-like illness during admission of the presumed
index patient. However, samples for influenza testing were not obtained from any of these
health care workers, so their role in possibly contributing to this transmission could not be
confirmed.
"Early identification and prolonged isolation precautions appear prudent in the care for infected
immunocompromised patients to prevent [hospital] influenza virus outbreaks. This study
confirmed that circulating H274Y-mutated A(H1N1) viruses can retain significant pathogenicity
and lethality, as shown in these elderly or immunocompromised patients with lymphocytopenia,
underlining the urgency for the introduction of new effective antiviral agents and therapeutic
strategies," the authors write.
They add that because the study consisted of a small number of patients, the findings require
careful interpretation and do not allow conclusions on the frequency of this complication in
hospital settings.
--------------------------------------------------------------------------------
Journal reference:
Jairo Gooskens; Marcel Jonges; Eric C. J. Claas; Adam Meijer; Peterhans J. van den Broek;
Aloys C. M. Kroes. Morbidity and Mortality Associated With Nosocomial Transmission of
Oseltamivir-Resistant Influenza A(H1N1) Virus. JAMA, 2009;0(2009):2009.297 [link]
Adapted from materials provided by JAMA and Archives Journals