Thursday, July 09, 2009, 19:15 EDT (7:15 PM EDT)
CDCHAN-00295-2009-07-09-ADV-N
Three Reports of Oseltamivir Resistant Novel Influenza A (H1N1) Viruses
Summary
On July 7,
2009 the World Health Organization announced the identification of a third
person with oseltamivir resistant novel H1N1 virus
infection.
All three
people fully recovered after uncomplicated illnesses and did not have contact
with each other. Two of the three people are reported to have developed
illness while taking oseltamivir preventatively after
an exposure to a close contact with novel influenza A (H1N). The third person
had no known exposure to oseltamivir.
Results
from ongoing testing of novel influenza A (H1N1) viruses indicate that oseltamivir resistance remains rare.
The interim
recommendations for the use of antiviral medications for chemoprophylaxis and
treatment have not been changed http://www.cdc.gov/h1n1flu/recommendations.htm.
Judicious
use of antiviral medications is recommended to reduce the possibilities of the
development and spread of antiviral resistant influenza viruses.
Use of zanamivir or oseltamivir should
be focused on treatment of persons with suspected novel
H1N1 influenza who are 1) hospitalized or 2) at higher risk for
complications due to influenza, even if hospitalization is not required.
Personal
hygiene practices such as hand washing and practices to prevent the spread of
an ill person's respiratory secretions should continue during treatment because
an infected person may continue to shed virus in respiratory secretions while
on therapy.
Use of oseltamivir for chemoprophylaxis should be reserved for
certain specific situations, such as when a person at high risk for
influenza-related complications is exposed to a person with influenza.
Monitoring
for antiviral resistance is ongoing and clinicians and state health departments
should continue to follow state and national guidance for submission and
testing of clinical specimens from persons with suspected novel influenza A
(H1N1) virus infection.
More
information will be provided as it becomes available.
Background
Since the
first cases of novel influenza A (H1N1) virus were detected in mid-April 2009,
more than 94,500 people with confirmed infection have been reported
worldwide.
Until
recently, all novel H1N1 viruses tested have been susceptible to oseltamivir and zanamivir
(neuraminidase inhibitors), and resistant to amantadine
and rimantadine (M-2 channel blockers, or adamantanes).
The World
Health Organization recently announced the identification of three persons with
oseltamivir-resistant novel influenza A (H1N1) virus
infection; all viruses had the same mutation that confers resistance, H274Y
(H275Y in N1 numbering), in the neuraminidase protein.
- On July 3, The Hong Kong
Department of Health reported a resistant virus isolated from a 16 year-old
girl who had a fever upon arrival at the Hong Kong International airport
on June 11, 2009. Her symptoms began prior to boarding the plane in
- On July 2, 2009, a person
infected with an oseltamivir-resistant novel
influenza A (H1N1) virus was reported from
- On June 29, 2009, the
Guidance
for the use of antiviral agents for novel influenza A
(H1N1) infection has not changed and is available at: http://www.cdc.gov/h1n1flu/recommendations.htm.
The use of
antiviral agents for treatment should be prioritized; zanamivir
or oseltamivir are recommended for the treatment of
persons with suspected novel H1N1influenza who are 1) hospitalized, or 2) at
higher risk for complications due to influenza, even if hospitalization is not
required.
Initiation
of antiviral therapy should be as early as possible, preferably within 48 hours
since symptom onset; however antiviral therapy for hospitalized persons is
recommended even if it is not possible to begin therapy until more than 48
hours after symptoms began.
Despite
treatment with antiviral agents, including treatment with the neuraminidase
inhibitors, patients may continue to shed influenza virus and some persons may
shed up to four or more days after beginning therapy. Therefore, patients
should continue good hand washing and respiratory hygiene practices during the
entire period on therapy to prevent the transmission of virus to close
contacts.
Antiviral
agents to prevent infection with novel influenza A (H1N1) virus should be used
judiciously.
Most people
who are infected with novel influenza A (H1N1) virus have had a self limited
illness and have recovered without the need for antiviral medications.
Inappropriate
use of oseltamivir for chemoprophylaxis could
contribute to the development of oseltamivir
resistance among novel influenza A (H1N1) viruses and the circulation of
resistant viruses in the community.
Use of antiviral
agents for chemoprophylaxis can be considered for persons at higher risk from
complications due to influenza, or for health care workers with an exposure to
influenza due to inadequate personal protective equipment.
Appropriate
administrative controls (e.g. having health care personnel stay home from work
when ill, and triaging for identification of potentially infectious patients)
and personal protective equipment should be used to reduce the need for
post-exposure chemoprophylaxis among health care workers.
Antiviral
agents are discouraged for prevention of illness in healthy children or adults
based on potential exposures in the community, school, camp or other settings.
In
addition, there is no safety data regarding long term or frequent use of
antiviral agents in children, and limited data for healthy adults.
Efforts to
monitor for antiviral resistance among novel influenza A (H1N1) viruses are
ongoing in the
Clinicians
and clinical laboratories should continue to test patients for novel influenza
A (H1N1) infection, especially hospitalized persons with suspect novel H1N1
influenza, and submit clinical specimens or viruses to the local public health
laboratory as described by each state health department.
State
laboratories should continue to test for novel influenza A (H1N1) and seasonal
influenza viruses and follow guidance issued by CDC for surveillance.
Reports on
antiviral resistance testing in the
TABLE:
Persons at Higher Risk for Complications of Novel Influenza A (H1N1) Virus Infection
Children younger than 5 years old. The risk for severe complications from seasonal influenza is highest among children younger than 2
Adults 65 years of age and older.
Persons with the following conditions:
Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), neurologic, neuromuscular, or metabolic disorders (including diabetes mellitus);
Immunosuppression, including that caused by medications or by HIV;
Pregnant women;
Persons younger than 19 years of age who are receiving long-term aspirin therapy;
Residents of nursing homes and other chronic-care facilities.
For
more information, please see the CDC website:
http://www.cdc.gov/h1n1flu/recommendations.htm
If you have
any questions about this Health Advisory, please call the Influenza Division,
Epidemiology and Prevention Branch at 404-639-3747.
After
normal business hours, contact CDC's duty officer through the CDC Director's
Emergency Operation Center (DEOC) at (770) 488-7100.
HAN Message Types
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- Health Update: Provides updated information regarding an incident or situation; unlikely to require immediate action. Example: HAN00309
- Info Service: Provides general information that is not necessarily considered to be of an emergent nature. Example: HAN00319
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