Possible recurrent pandemic (H1N1) 2009 infection, Israel.
Article Type: Letter to the editor
Subject: Swine influenza (Risk factors)
Swine influenza (Diagnosis)
Swine influenza (Care and treatment)
Swine influenza (Demographic aspects)
Swine influenza (Research)
Polymerase chain reaction (Usage)
Authors: Kopel, Eran
Mandelboim, Michal
Amitai, Ziva
Grotto, Itamar
Hindiyeh, Musa
Kaliner, Ehud
Mendelson, Ella
Volovik, Irina
Pub Date: 08/01/2010
Publication: Name: Emerging Infectious Diseases Publisher: U.S. National Center for Infectious Diseases Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2010 U.S. National Center for Infectious Diseases ISSN: 1080-6040
Issue: Date: August, 2010 Source Volume: 16 Source Issue: 8
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: Israel Geographic Code: 7ISRA Israel
Accession Number: 237533372
Full Text: To the Editor: We report 2 cases of possible recurrent laboratoryconfi rmed infection with pandemic (H1N1) 2009 virus in Israel. Patient 1, a 24-year-old man, had Noonan syndrome (1,2). He was hospitalized on August 10, 2009, because of high-grade fever and cough. At admission, a nasopharyngeal specimen was collected for pandemic (H1N1) 2009 virus real-time reverse transcription-PCR (RT-PCR) (ABI 7500; Applied Biosystems, Foster City, CA, USA) for the pandemic hemagglutinin gene; a validated in-house protocol developed at Israel Central Virology Laboratory was used, as previously described (3). Briefly, the in-house assay was validated against the assay for pandemic (H1N1) 2009 virus developed by the Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA). The in-house assay was as sensitive as the CDC assay; however, the in-house primers and probes were more specific for detecting pandemic (H1N1) 2009 virus with 105% amplification efficiency of viral RNA that was logarithmically serially diluted. In addition, of 100 samples tested side by side with the in-house and CDC assays, 75 samples were positive by both assays, and 25 were negative by both assays; thus, the sensitivity and specificity of the in-house assay were 100%.

The patient was not treated with neuraminidase inhibitors and did not require supportive treatment; after 1 day of hospitalization, he was discharged with a diagnosis of upper respiratory tract infection. The laboratory subsequently reported the RTPCR as positive for pandemic (H1N1) 2009 virus. On November 22, the man was hospitalized again for dyspnea and fever. The RT-PCR result from a nasopharyngeal sample collected at admission was positive. Hemagglutination-inhibition assay demonstrated a high titer (320) of serum antibody against pandemic (H1N1) 2009 virus in a blood sample taken at admission. The patient took oseltamivir for 5 days, and his condition markedly improved. Result of a repeat RT-PCR at discharge was negative.

An identical neuraminidase gene sequence was detected during both illness episodes (August and November). The specimens were also tested with an experimental RT-PCR assay for rapid detection of the oseltamivir resistance mutation H275Y on the pandemic neuraminidase gene (4). For specimens collected during both episodes, the virus was oseltamivir sensitive.

Patient 2, a 13.5-year-old boy, had severe cerebral palsy. On July 27, 2009, high-grade fever with dyspnea developed. He was treated as an outpatient for 5 days with oseltamivir and clinically improved. However, on August 11, he had fever with respiratory distress and was hospitalized. RTPCR for pandemic (H1N1) 2009 virus was positive on August 14. A second course of oseltamivir was administered for 10 days with the dosage adjusted for age and doubled from that of the previous regimen. Further testing with the experimental rapid RT-PCR indicated the viral strain had the oseltamivir resistance mutation. On September 14, RT-PCR was negative.

On December 11, the boy was again hospitalized because of respiratory distress and high-grade fever. On December 14, RT-PCR was positive for pandemic (H1N1) 2009 virus, and a 5-day regimen of oseltamivir was started. Another specimen taken the same day was negative. A high serum antibody titer (320) to pandemic (H1N1) 2009 virus was measured by hemagglutination-inhibition assay on December 16; no oseltamivir resistance mutation was found. Additional laboratory testing included a complete panel for respiratory viruses, which was negative for human metapneumovirus; respiratory syncytial virus; adenovirus; seasonal influenza virus types A and B; and parainfluenza virus types 1, 2, and 3.

These 2 cases of possible recurrent pandemic (H1N1) 2009 infection demonstrated a wide interval between illness episodes. Neither patient had accompanying immunodeficiency, and both had antibody titers far beyond the accepted seroprotective threshold for influenza (5), albeit ineffective. These titers probably resulted from primary infection rather than from subclinical exposure, which manifests itself as a lower titer by order of magnitude (6,7).

Virus clearance was not laboratory confirmed for patient 1 after the first episode because no samples were taken after hospital discharge. Patient 2 had both positive and negative RTPCRs for pandemic (H1N1) 2009 virus (Table) from samples collected the same day during the second hospitalization, which also may disprove reinfection. The positive result could be explained by laboratory contamination during the RT-PCR processing that indicated a false-positive result. However, contamination is unlikely because each run of the RT-PCR was routinely accompanied by runs of negative controls (that contain water) to rule out such contamination. Nonanalytic factors such as specimen misidentification also are unlikely because the central virology laboratory, which is the national reference center, has an ISO-9000 qualification from the Standards Institution of Israel (www.sii.org.il/20-en/SII_EN.aspx). Furthermore, no other respiratory virus was found by laboratory testing at that time. The patient was infected with an oseltamivir-resistant pandemic (H1N1) 2009 virus during the first illness episode and with an oseltamivir-sensitive virus during the second episode and had 2 RT-PCRs with negative results between the episodes.

The novel pandemic influenza virus may be able to reinfect certain chronically ill persons. Caregivers should be aware of this trait when considering the differential diagnosis of influenza-like illness in a patient with a documented, and even treated, pandemic (H1N1) 2009 infection.


We thank the medical team and administrative staff of the epidemiology unit, the respiratory intensive care unit, and the pediatric intensive care unit of Sheba Medical Center, Tel Hashomer, for their cooperation. We also thank Shalom Bronstein for proofreading.


(1.) Noonan JA. Hypertelorism with Turner phenotype. A new syndrome with associated congenital heart disease. Am J Dis Child. 1968;116:373-80.

(2.) Allanson JE. Noonan syndrome [review]. J Med Genet. 1987;24:9-13.

(3.) Panning M, Eickmann M, Landt O, Monazahian M, Olschlager S, Baumgarte S, et al. Detection of influenza A(H1N1)v virus by real-time RT-PCR. Euro Surveill. 2009;14:pii:19329.

(4.) Hindiyeh M, Ram D, Mandelboim M, Meningher T, Hirsh S, Robinov J, et al. Rapid detection of influenza A pandemic (H1N1) 2009 virus neuraminidase resistance mutation H275Y by real-time RTPCR. J Clin Microbiol. 2010;48:1884-7. DOI:10.1128/JCM.02540-09

(5.) Potter CW, Oxford JS. Determinants of immunity to influenza infection in man. Br Med Bull. 1979;35:69-75.

(6.) Greenberg ME, Lai MH, Hartel GF, Wichems CH, Gittleson C, Bennet J, et al. Response to a monovalent 2009 influenza A (H1N1) vaccine. N Engl J Med. 2009;361:2405-13.

(7.) Nolan T, McVernon J, Skeljo M, Richmond P, Wadia U, Lambert S, et al. Immunogenicity of a monovalent 2009 influenza A(H1N1) vaccine in infants and children: a randomized trial. JAMA. 2009;303:3746.

Eran Kopel, (1) Michal Mandelboim, (1) Ziva Amitai, Itamar Grotto, Musa Hindiyeh, Ehud Kaliner, Ella Mendelson, and Irina Volovik

Author affiliations: Ministry of Health, Tel Aviv, Israel (E. Kopel, Z. Amitai, E. Kaliner, I. Volovik); Ministry of Health, Ramat Gan, Israel (M. Mandelboim, M. Hindiyeh, E. Mendelson); and Ministry of Health, Jerusalem, Israel (I. Grotto)

Address for correspondence: Eran Kopel, Tel Aviv District Health Office, Ministry of Health, 12 Ha'arba'ah St, POB 20301, Tel Aviv 61203, Israel; email: eran.kopf@telaviv.health.gov.il 1These authors contributed equally to this article.

DOI: 10.3201/eid1608.100436
Table. Real-time RT-PCR for pandemic (H1N1) 2009 virus and results
of experimental assay * for oseltamivir resistance mutation H275Y,
Israel, 2009 ([dagger])

                 Patient 1                Patient 2

                    Oseltamivir              Oseltamivir
                    resistance/              resistance/
Date     RT-PCR     sensitivity   RT-PCR     sensitivity

Aug 10   Positive   Sensitive     --         --
Aug 14   --         --            Positive   Resistant
Aug 19   --         --            Positive   Resistant
Sep 1    --         --            Positive   Resistant
Sep 14   --         --            Negative   --
Nov 22   Positive   Sensitive     Negative   --
Nov 29   Negative   --            --         --
Dec 14   --         --            Positive   Sensitive
Dec 14   --         --            Negative   --
Dec 17   --         --            Negative   --
Dec 21   --         --            Negative   --

* Source: (4).

([dagger]) RT-PCR, reverse transcription-PCR; -, not tested.
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