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Published Date: 2009-08-15 19:00:06
Subject: PRO/AH/EDR> Influenza pandemic (H1N1) 2009 (31): drug resistance
Archive Number: 20090815.2900

INFLUENZA PANDEMIC (H1N1) 2009 (31): DRUG RESISTANCE
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Date: Fri 14 Aug 2009
Source: MMWR Dispatch, 14 Aug 2009 / 58 (Dispatch); 1-4
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0814a1.htm?s_cid=mm58d0814a1_e>

Oseltamivir-resistant influenza pandemic (H1N1) 2009 virus infection in 2
immunosuppressed patients
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Influenza (H1N1) 2009 virus infection continues to cause illness and death
among persons worldwide. Immunosuppressed patients with influenza virus
infection can shed virus for prolonged periods, increasing the chances for
development of drug resistance (1-3). On 6 Aug 2009, the Centers for
Disease Control and Prevention (CDC) detected evidence of resistance to the
antiviral medication oseltamivir in 2 severely immunosuppressed patients
with novel influenza A (H1N1) virus [that is, Influenza pandemic (H1N1)
2009 virus] infection in Seattle, Washington. The 2 patients were treated
in 2 different hospitals, and their cases were not epidemiologically
linked. Both were being treated with oseltamivir for novel influenza A
(H1N1) virus infection and had prolonged viral shedding. In both patients,
the virus was documented as initially susceptible to oseltamivir, and
resistance developed subsequently during treatment with the drug. Testing
of viral RNA from both patients by pyrosequencing detected a mutation that
results in a histidine-to-tyrosine substitution at position 275 (H275Y) in
the neuraminidase, known to be associated with oseltamivir resistance
(4,5). The results were confirmed by pyrosequencing, sequencing of the
neuraminidase gene, and neuraminidase inhibition testing of virus isolates
on 11 Aug 2009. One patient's symptoms resolved after treatment with
oseltamivir, and the other patient was receiving treatment with zanamivir
and ribavirin as of 13 Aug 2009. An investigation of health care personnel
(HCP) contacts and other close contacts revealed no evidence of virus
transmission. This report summarizes the case histories and resulting
investigations and highlights the importance of 1) close monitoring for
antiviral drug resistance among immunosuppressed patients receiving
treatment for novel influenza A (H1N1) virus infection and 2) the
implications for infection control.

Case reports
------------
Case 1. A teenaged male was diagnosed with leukemia in November 2008 and
subsequently received outpatient immunosuppressive chemotherapy. On 29 Apr
2009, he was hospitalized for a hematopoietic stem cell transplant, which
he received on 7 May 2009. He received immunosuppressive treatment prior to
his transplantation and remained hospitalized in a single-patient room
after the transplantation. On 31 May 2009, he developed fever, mild cough,
and rhinorrhea, was placed on droplet and contact precautions, and HCP
began using respirators (fit-tested N95 or higher-level protection) for his
care. A nasal wash specimen collected on 31 May 2009 tested positive for
novel influenza A (H1N1) virus by real-time reverse
transcription-polymerase chain reaction (rRT-PCR) at the University of
Washington Virology Laboratory. On 1 Jun 2009, the patient was enrolled in
an influenza antiviral treatment study and he began a 10-day course of
oseltamivir. However, on 4 Jun 2009, novel influenza A (H1N1) virus was
detected again by rRT-PCR and viral culture in nasal wash specimens, and
oseltamivir treatment was extended to a 20-day course, to 20 Jun 2009. The
patient improved and was discharged to a nearby apartment on 7 Jun 2009.
Virus again was detected in nasal wash specimens on 11 Jun 2009. On 7 Jul
2009, a nasal wash specimen collected for routine follow-up on an
outpatient basis was positive for novel influenza A (H1N1) virus by
rRT-PCR; oseltamivir therapy was resumed on 8 Jul 2009.

The patient remained well until 14 Jul 2009, when he was hospitalized with
fever and treated for coagulase-negative staphylococcal infection of an
indwelling central venous catheter. A nasal wash specimen collected on 14
Jul 2009 tested positive for novel influenza A (H1N1) virus by rRT-PCR, and
his oseltamivir was increased to a high dose, 150 mg orally, twice a day.
Increased rhinorrhea and mild cough were noted on 16 Jul 2009. The patient
was discharged on oseltamivir on 18 Jul 2009.

Because of prolonged shedding of novel influenza A (H1N1) virus and
suspected oseltamivir resistance, nasal wash specimens previously collected
from the patient were sent to CDC for antiviral resistance testing and
arrived on 5 Aug 2009. On 6 Aug 2009, pyrosequencing at CDC of viral RNA
from a specimen collected on 4 Jun 2009 revealed susceptibility to
oseltamivir. However, pyrosequencing of a follow-up specimen collected on
30 Jul 2009 indicated oseltamivir resistance, based on detection of the
H275Y mutation (4,5). Treatment of the patient with oseltamivir was stopped
on 6 Aug 09, when CDC pyrosequencing results from the specimens became
available. Because the patient was asymptomatic, no further treatment was
indicated.

On 10 Aug 2009, CDC received previously collected virus isolates from the
patient for pyrosequencing on 11 Aug 2009, which confirmed the previous
results. A novel influenza A (H1N1) virus isolate from a specimen collected
on 31 May 2009 was identified as susceptible to oseltamivir by
pyrosequencing at CDC, but viruses isolated from specimens collected on 11
Jun 2009 and 14 Jul 2009 had the H275Y mutation, indicating oseltamivir
resistance.

Seattle-King County health department investigators interviewed hospital
infection-control staff and the patient's family members and visitors.
Surveillance for influenza-like illness (ILI) among staff members is
standard policy at the hospital where the patient was treated. No cases of
ILI were reported among approximately 100 HCP contacts of the patient.
Active surveillance, involving personal interviews of HCP contacts during
the 2 weeks before diagnosis of oseltamivir resistance did not identify any
HCP with ILI.

After each hospital discharge, the patient lived under voluntary home
isolation according to standard protocol for patients in the
post-hematopoietic stem cell transplant (HSCT) period; he did not attend
any school. When traveling in public, the patient reported wearing a
surgical mask per protocol for immunosuppressed HCST recipients and
avoiding close contact with other persons and crowds. None of the 12 family
member contacts or other persons who had visited the patient while he was
in isolation reported symptoms of ILI.

Case 2: A female patient in her 40s who had a hematopoietic stem cell
transplant for leukemia had a recurrence of leukemia in December 2008. She
underwent 2 cycles of immunosuppressive chemotherapy during March--April
2009. On 21 Jun 2009, she was admitted to the hospital for further
chemotherapy; she also had developed a fever and symptoms of an upper
respiratory infection. She was placed in a single-patient room with droplet
and contact precautions, and a nasal wash specimen was obtained for direct
fluorescent antibody staining (DFA) and viral culture. The DFA result was
indeterminate because of an inadequate cellular specimen; however, on 26
Jun 2009, the University of Washington Virology Laboratory reported
isolation of influenza A virus from the specimen. Antiviral treatment with
high-dose oseltamivir (150 mg orally, twice a day) and rimantadine (100 mg
orally, twice a day) was administered during 26 Jun 26--1 Jul 2009. On 3
Jul 2009, the viral isolate was identified as novel influenza A (H1N1), and
high-dose oseltamivir and rimantadine were restarted. The patient's
respiratory status worsened, and she required supplemental oxygen for
hypoxia. Novel influenza A (H1N1) virus was isolated from additional nasal
wash specimens collected on 6 Jul 2009 and 14 Jul 2009, and from
bronchoalveolar lavage specimens obtained on 16 and 28 Jul 2009. Because of
prolonged viral shedding, specimens were sent to CDC on 4 Aug 2009 for
antiviral susceptibility testing. Treatment with inhaled zanamivir was
attempted, but was poorly tolerated, and oseltamivir was continued.

On 6 Aug 2009, CDC determined that pyrosequencing of viral RNA from the 1st
clinical specimen collected on 21 Jun 2009 did not detect the H275Y
mutation. However, the mutation was detected by pyrosequencing of viral RNA
from a nasal wash specimen collected on 28 Jul 2009. Treatment of the
patient with oseltamivir was discontinued when results became available.

Treatment with inhaled zanamivir after identification of oseltamivir
resistance again was attempted but poorly tolerated. On 7 Aug 2009,
intravenous zanamivir, acquired through an emergency investigational new
drug application for compassionate use, and aerosolized ribavirin therapy
were initiated. As of 13 Aug 2009, the patient remained symptomatic and
hospitalized on intravenous zanamivir and had been switched to oral
ribavirin because of intolerance of aerosolized ribavirin. The patient's
hospital course was complicated by prolonged neutropenia and protracted
bone marrow recovery, neutropenic fever, coagulase-negative Staphylococcus
bacteremia, and _Pneumocystis jirovecii_ pneumonia. On 10 Aug 2009, CDC
received other previously collected virus isolates from this patient for
testing, and pyrosequencing of a virus isolated from a specimen collected
on 14 Jul 2009 had the H275Y mutation, confirming oseltamivir resistance.

The patient was hospitalized in a single-patient room upon admission on 21
Jun 2009. She was initially placed on droplet and contact precautions.
Immediately after confirmation of novel influenza A (H1N1) virus infection,
use of N95 repirators by HCP also was implemented. Active surveillance for
respiratory illness among staff members is routine at the hospital where
the patient was treated, and no cases of ILI or other acute respiratory
illness were reported among the approximately 200 HCP contacts who cared
for the patient. No breaches of personal protective equipment
recommendations (including use of fit-tested N-95 respirators) were
reported among HCP contacts caring for this patient.

Testing of clinical specimens for oseltamivir resistance
--------------------------------------------------------
CDC has tested virus isolates or clinical specimens collected from 37
additional Washington residents with confirmed novel influenza A (H1N1)
virus infection during 26 Apr-30 Jul 2009. None of these viruses had
evidence of the H275Y mutation. As of 11 Aug 2009, of the 670 novel
influenza A (H1N1) viruses collected since April 2009 in the United States
and tested at CDC, 318 had been tested for oseltamivir and zanamivir
resistance by neuraminidase inhibition assay, and 352 clinical specimens
had been screened for oseltamivir resistance for the H275Y mutation by
pyrosequencing. No other oseltamivir-resistant viruses had been identified.
Oseltamivir-resistant viruses isolated from both patients described in this
report were determined to be susceptible to zanamivir by neuraminidase
inhibition assay at CDC. Sequence analysis of the neuraminidase gene of
these oseltamivir-resistant viruses showed that oseltamivir resistance was
not the result of gene reassortment with seasonal influenza A (H1N1) virus.

[byline: J Englund, MD, D Zerr, MD, J Heath, Seattle Children's Hospital,
Univ of Washington, and Fred Hutchinson Cancer Research Center; S Pergam,
MD, J Kuypers, PhD, J Yager, MD, M Boeckh, MD, D Mattson, N Whittington, E
Whimbey, MD, Univ of Washington Medical Center and Fred Hutchinson Cancer
Research Center; J Duchin, MD, Public Health --- Seattle and King County,
Washington. T Uyeki, MD, V Deyde, PhD, M Okomo-Adhiambo, PhD, T Sheu, A
Trujillo, A Klimov, PhD, ScD, L Gubareva, MD, PhD, Influenza Div, National
Center for Immunization and Respiratory Diseases; M Kay, DVM, EIS Officer,
CDC.]

MMWR editorial note:
--------------------
This report describes oseltamivir-resistant novel influenza A (H1N1) virus
infection in 2 severely immunosuppressed patients who were treated with
oseltamivir for acute illness symptoms of laboratory-confirmed influenza.
Initially, both patients were infected with oseltamivir-susceptible
viruses; oseltamivir resistance developed later during antiviral treatment.
The 2 patients were not epidemiologically linked and were treated at
different hospitals. No evidence was found that HCP or other patient
contacts developed ILI caused by oseltamivir-resistant novel influenza A
(H1N1) virus infection.

Immunosuppressed patients are at increased risk for complications of
influenza and are recommended for annual influenza vaccination, although
the immune response to vaccination can be decreased in some persons (6,7).
In otherwise healthy adults with seasonal influenza virus infection, viral
shedding generally resolves within 7 days, compared with immunosuppressed
patients, who can experience prolonged viral shedding for weeks to months.
Antiviral resistance can develop during treatment of influenza in these
patients, and prolonged viral shedding (1,2) of up to 18 months has been
reported, including shedding of oseltamivir-resistant seasonal influenza A
virus for more than 1 year (3). Clinicians caring for immunosuppressed
patients with novel influenza A (H1N1) virus infection should be aware of
the potential for development of antiviral drug resistance during therapy
and prolonged viral shedding. Recommendations for prevention and control of
seasonal influenza among hematopoietic stem cell transplant recipients,
their family members, and HCP have been published (8). Strict adherence to
recommended personal protective equipment and infection-control measures is
advised until an immunosuppressed patient with influenza virus infection
has serial respiratory specimens that remain negative when tested by both
rRT-PCR and viral culture. Interim infection-control guidance for novel
influenza A (H1N1) is available on the CDC website, available at
<http://www.cdc.gov/h1n1flu/guidelines_infection_control.htm>.

Only sporadic cases of oseltamivir resistance associated with the H275Y
mutation in the neuraminidase have been detected in immunocompetent persons
exposed to oseltamivir (9). As of 11 Aug 2009, no evidence had been found
of ongoing transmission of oseltamivir-resistant novel influenza A (H1N1)
virus in the United States or elsewhere in the world. The public health
risk of virus transmission from these 2 immunosuppressed cases with
oseltamivir-resistant novel influenza A (H1N1) virus infection appears to
be low. Currently, enhanced surveillance for oseltamivir resistance among
novel influenza A (H1N1) virus strains isolated from outpatients and
hospitalized patients is being conducted in Washington in collaboration
with CDC. The 2 cases in immunosuppressed patients described in this report
and sporadic cases of oseltamivir resistance in persons with oseltamivir
exposure, highlight the need for ongoing global virologic surveillance and
monitoring of antiviral resistance (10).

All circulating novel influenza A (H1N1) virus strains worldwide remain
susceptible to oseltamivir and zanamivir but resistant to amantadine and
rimantadine. CDC continues to recommend oseltamivir or zanamivir for
treatment of all hospitalized patients with suspected or confirmed novel
influenza A (H1N1) virus infection and for outpatients at increased risk
for influenza-related complications (for example, young children, pregnant
women, and persons with certain chronic medical conditions) with suspected
or confirmed novel influenza A (H1N1) virus infection. Novel influenza A
(H1N1) virus strains with the H275Y mutation are susceptible to zanamivir.
Therefore, in immunosuppressed patients with oseltamivir-resistant novel A
(H1N1) virus infection, zanamivir should be considered the antiviral
treatment of choice; however, zanamivir is not recommended for persons with
underlying airway disease. Additional interim guidance on the use of
antiviral medications for the treatment and prevention of novel influenza A
(H1N1) virus infection is available on the CDC website, available at
<http://www.cdc.gov/h1n1flu/recommendations.htm>.

References:
-----------
1. Klimov AI, Rocha E, Hayden FG, Shult PA, Roumillat LF, Cox NJ. Prolonged
shedding of amantadine-resistant influenzae A viruses by immunodeficient
patients: detection by polymerase chain reaction-restriction analysis. J
Infect Dis 1995; 172: 1352-5.
2. Ison MG, Gubareva LV, Atmar RL, Treanor J, Hayden FG. Recovery of
drug-resistant influenza virus from immunocompromised patients: a case
series. J Infect Dis 2006; 193: 760-4.
3. Weinstock DM, Gubareva LV, Zuccotti G. Prolonged shedding of
multidrug-resistant influenza A virus in an immunocompromised patient. N
Engl J Med 2003; 27; 348: 867-8.
4. Deyde VM, Gubareva LV. Influenza genome analysis using pyrosequencing
method: current applications for a moving target. Expert Rev Mol Diagn
2009; 9: 493-509.
5. WHO. CDC pyrosequencing assay to detect H275Y mutation in the
neuraminidase of novel A (H1N1) viruses. Available at
<http://www.who.int/csr/resources/publications/swineflu/NA_DetailedPyrosequencing_20090513.pdf>.

6. CDC. Prevention and control of seasonal influenza with vaccines:
recommendations of the Advisory Committee on Immunization Practices (ACIP),
2009. MMWR 2009; 58(No. RR-8).
7. Kunisaki KM, Janoff EN. Influenza in immunosuppressed populations: a
review of infection frequency, morbidity, mortality, and vaccine responses.
Lancet Infect Dis 2009; 9: 493-504.
8. CDC. Guidelines for preventing opportunistic infections among
hematopoietic stem cell transplant recipients: recommendations of CDC, the
Infectious Disease Society of America, and the American Society of Blood
and Marrow Transplantation. MMWR 2000; (No. RR-10).
9. WHO. Pandemic (H1N1) 2009. Update 60. Laboratory-confirmed cases of
pandemic (H1N1) 2009 as officially reported to WHO by states parties to the
IHR (2005) as 31 Jul 2009. Available at
<http://www.who.int/csr/don/2009_08_04/en/index.html>.
10. Sheu TG, Deyde VM, Okomo-Adhiambo M, et al. Surveillance for
neuraminidase inhibitor resistance among human influenza A and B viruses
circulating worldwide in 2004--2008. Antimicrob Agents Chemother 2008; 52:
3284-92.

--
communicated by:
ProMED-mail
<promed@promedmail.org>

[It is perhaps not unexpected that uncontained replication of influenza
pandemic (H1N1) 2009 virus in immunosuppressed individuals treated with
high doses of oseltamivir would favour the appearance of resistant virus.
It is reassuring that in the cases described above resistance was conferred
by the H275Y mutation in the NA gene and that the resistant viruses remain
sensitive to inhibition by the alternate neuraminidase inhibitor zanamivir.
Oseltamivir resistance is not uniquely associated with immunosuppression.
There have been previous reports, the most recent concerning a single
patient in a care home in Hong Kong: see
<http://www.news.gov.hk/en/category/healthandcommunity/090814/txt/090814en05006.htm>.
- Mod.CP]

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