Influenza A(H5N1) Virus Infection in a Child With Encephalitis Complicated by Obstructive Hydrocephalus
Influenza A(H5N1) Virus Infection in a Child With Encephalitis Complicated by Obstructive Hydrocephalus
Gannon Chun Kit Mak 1 2
Mike Yat-wah Kwan 0
Chris Ka Pun Mok 1
Janice Yee Chi Lo 2
Malik Peiris 1
Chi Wai Leung 0
0 Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital , Hong Kong Special Administrative Region , China
1 HKU-Pasteur Research Pole, School of Public Health, University of Hong Kong
2 Public Health Laboratory Services Branch, Centre for Health Protection, Department of Health
A 2-year-old boy with highly pathogenic avian influenza A(H5N1) virus infection with minimal respiratory symptoms developed encephalitis complicated by obstructive hydrocephalus. Viral RNA was detectable in cerebrospinal fluid. The virus belonged to H5N1 clade 184.108.40.206b and had acquired the mammalian adaptation mutation PB2 Q591K.
A 2-year-old boy developed fever, runny nose, and productive
cough on 23 May 2012 (day 1 of illness) in Guangdong province.
He returned to Hong Kong on 26 May and sought outpatient
medical attention. On 28 May (day 6 of illness), he developed
convulsions and was admitted to the Caritas Medical Centre
with a diagnosis of suspected encephalitis. His chest radiograph
was unremarkable. A nasopharyngeal aspirate was found to
be positive for influenza A by real-time reverse-transcription
polymerase chain reaction (RT-PCR), negative for H1 and
H3, and subsequently subtyped to be H5N1 [
]. The child was
transferred to the Intensive Care Unit of the Infectious Disease
Centre at Princess Margaret Hospital for isolation and further
management. Oseltamivir therapy was commenced on 30 May
(day 8 of illness) at a dose of 60 mg orally twice daily for a child
weighing 11.9 kg—that is, double the dose recommended for
uncomplicated influenza. The parents denied consent for a
lumbar puncture at this stage. Epidemiological investigation
revealed that the boy had visited a sidewalk wet market with live
poultry in Guangzhou in mid-May. The boy’s parents remained
asymptomatic and clinical specimens collected from them were
negative for influenza A.
Computed tomography of the brain performed on day 6 of
illness showed no focal lesion and no displacement of midline
structures, and the ventricles were not dilated (Figure 1A).
Magnetic resonance imaging of the brain on day 11 of illness
showed moderate obstructive hydrocephalus with
transependymal flow of the cerebrospinal fluid (CSF) evidenced by the dilated
bilateral lateral ventricles and the third ventricles (Figure 1B).
The fourth ventricle was not dilated. The level of obstruction was
at the cerebral aqueduct. An external ventricular catheter was
inserted to relieve the obstructive hydrocephalus. Examination
of the drained ventricular CSF on day 11 of illness revealed a red
blood cell count 242 cells/μL, white blood cell count 165 cells/μL
with lymphocyte predominance, protein 1.44 g/L, and glucose
2.4 mmol/L. A small fragment of brain tissue showed histological
features of meningoencephalitis, and virus RNA was detectable
at a borderline level (CT39). PCR for herpes simplex virus type
1 and 2 DNA and RT-PCR for enterovirus RNA were repeatedly
negative in the CSF specimens and in the brain biopsy.
Serial specimens of CSF, nasopharyngeal aspirate (NPA),
rectal swab, stool, urine, plasma, and serum were tested by
real-time quantitative RT-PCR (qPCR) targeting M gene for
influenza A virus and the hemagglutinin (HA) gene for H5N1
virus (Supplementary Methods; Table 1). The qPCR assay for
the H5 gene was more sensitive than for the influenza M gene.
CSF collected on day 11 and 13 as well as plasma on day 11 had
detectable viral RNA (M gene and H5 gene), albeit at low viral
load. In view of detection of virus RNA in CSF, the reported
low CSF penetration of oseltamivir [
], known good intrathecal
penetration of amantadine [
], and the virus genetic sequence
(see below) without known mutations in the M2 gene associated
with amantadine resistance, oral amantadine therapy (40 mg
orally twice daily) was added to oseltamivir on day 14 of illness.
The amantadine dosage was increased to 50 mg orally twice
daily on day 27. In view of persistence of viral RNA in
nasopharyngeal aspirates, ribavirin at a dose of 180 mg was given
intravenously every 6 hours from day 27. The child received
oseltamivir for 25 days, amantadine for 17 days, and ribavirin
for 5 days. Given the late commencement of amantadine and
ribavirin, their therapeutic contribution remains unclear. The
ventricular drain was removed on day 35. The child made a
complete recovery and was discharged from hospital on 5 July
with satisfactory clinical condition. There were no neurological
sequelae or developmental delay detected during subsequent
Levels of monocyte chemoattractant protein 1, monokine
induced by interferon gamma, and CXCL 10 (interferon
gamma-induced protein 10) were assayed on the patient serum and
CSF collected on day 11 of illness (Supplementary Methods).
Serum samples from 6 controls (aged 6, 7, 8, 36, 42, and
47 years, collected from other noninfectious clinical indications
and anonymized for chemokine testing) were also assayed
(Supplementary Figure 1).
A madin darby canine kidney cell culture virus isolate
designated A/Hong Kong/5923/2012 (H5N1) (abbreviated to
H5N1/5923 hereafter) was obtained from an NPA specimen
collected on day 6 of illness. The virus was fully genetically sequenced
and phylogenetic analysis showed that the virus belonged to clade
220.127.116.11b in all 8 gene segments. The PB1 and PA gene segments
of clade 18.104.22.168b viruses cluster also with corresponding genes of
H5N6 viruses (Supplementary Figure 2). The H5N1/5923 virus
had a Q591K amino acid substitution in the PB2 protein in
specimens collected at day 6 and day 11 of illness. The HA1-HA2
connecting peptide possessed a multibasic amino acid sequence
(PQIERRRRKR*GLF), which is common in clade 22.214.171.124b H5N1
viruses and characteristic of HPAI viruses. Mature HA protein
has amino acid residues E190, Q226, and G228 (H3
numbering), indicating an avian-like receptor specificity (Supplementary
]. There were no mutations in the viral neuraminidase
(NA) or M2 genes associated with resistance to NA inhibitors or
adamantanes (Supplementary Table). The virus NA and M genes
from NPA specimens collected on day 15, 17, 19, 21, and 22 of
illness was also sequenced directly from the clinical specimen,
and no known resistance mutations to NA inhibitors or
adamantanes were detected (Supplementary Table).
Patients infected with H5N1 present primarily with acute
respiratory illness [
]. To our knowledge, there are only 2 other
case reports of H5N1 infections with major manifestations of
central nervous system (CNS) disease [
] but neither with
hydrocephalus. The first was a 4-year-old boy who presented
with fever, headache, and diarrhea in Vietnam. He had no
respiratory symptoms at initial admission and had a normal chest
radiograph. He later developed a cough and had mild crackles
and wheezing on auscultation. He became drowsy and then
comatose. CSF examination revealed a moderately elevated
CSF protein level but no increase in white cells. He progressed
to respiratory failure and died. The diagnosis was acute
encephalitis. Retrospective investigation as part of a study of
encephalitis of unknown etiology yielded an influenza A(H5N1) virus
isolate from the stored CSF specimen. The boy’s sister had died
of a similar illness a few days previously . A second patient
was a young adult who presented with multilobar pneumonia
progressing to diffuse encephalitis, leading to a fatal outcome
HPAI H5N1 virus may enter the CNS via the blood
circulation. Alternatively, virus from the nasopharynx may traverse
the cribriform plate and enter the basal subarachnoid space with
subsequent retrograde spread from the cisterna magna into the
ventricular CSF space through the foramina of Luschka and
Magendie. Spread of HPAI H5N1 virus to the brain along the
olfactory nerves and via the cribriform plate has been reported
BRIEF REPORT • CID 2018:66 (1 January) • 137
in experimentally infected ferrets [
]. In this patient,
inflammation resulting in acute ependymitis may have led to obliteration
of the cerebral aqueduct between the third and fourth
ventricles, the narrowest part of the ventricular system, resulting in
Patients infected with H5N1 reportedly rarely had
detectable viral RNA in the respiratory tract for >3 weeks [
]. In the
present study, viral RNA was detected in a patient with H5N1
from NPA up to day 30 after symptom onset. The RT-PCR cycle
threshold value may be a useful indicator of response to therapy.
The serum chemokine levels in the patient at day 11 after onset
of illness were not markedly different to controls. Previous
studies have reported that chemokine levels were higher in fatal
rather than nonfatal patients with H5N1 disease [
this patient, pathology was primarily in the CNS rather than
the lung; it is therefore interesting that the chemokine level in
the patient’s CSF was markedly elevated in comparison to the
level in the serum sample collected on the same day, providing
additional evidence of inflammation within the CNS
compartment (Supplementary Figure 1).
138 • CID 2018:66 (1 January) • BRIEF REPORT
Previous studies have shown that specific amino acid
substitutions in PB2 of avian influenza viruses enhance replication
competence in mammalian cells and are recognized
mammalian adaptation markers. In contrast to other clade 126.96.36.199
H5N1 viruses, the H5N1/5923 virus from our patient had a PB2
Q591K mutation. This amino acid substitution has been shown
to increase the replication and pathogenicity of avian H5N1,
H9N2, and H7N9 viruses in mammals in a manner
analogous to previously reported mammalian adaptation signatures
E627K and D701N [
]. However, while the PB2-E627K
mediates the virus dissemination to the brain after infection, a
similar role for PB2-Q591K has not yet been reported in
experimental mammalian models, although this remains plausible.
The genetic analysis of the virus HA suggests that the virus
had a preference for binding α(2–3)–linked sialic acids found
in avian species. Adult humans have a preponderance of
α(26)–linked sialic acids in their upper respiratory tract, and H5N1
virus disease is believed to take place when the virus gains access
to the alveolar epithelium where α(2-3)–linked sialic acids are
present. However, it has been reported that young children
differ in this respect and have a preponderance of α(2-3)–linked
sialic acids in their upper respiratory tract [
]. These findings
need independent confirmation. However, it is interesting to
speculate whether this may have predisposed this child to
infection with this avian virus infecting the upper respiratory tract
and subsequently passing via the cribriform plate to invade the
CNS. In this patient, it is possible that host (young age, genetic
susceptibility) or viral determinants, or both, contributed to the
unusual CNS manifestations.
In conclusion, we report influenza A(H5N1) infection in a
child presenting as encephalitis and progressing to obstructive
hydrocephalus, preceded by mild upper respiratory symptoms.
In many instances, such patients may be primarily investigated
for typical causes of CNS disease rather than for influenza
A. This case report highlights the need to have a high index of
suspicion and the need to investigate patients with CNS disease
for HPAI H5N1 in areas where this virus is endemic in poultry
and in travelers returning from such areas, even when
respiratory symptoms are not the prominent presenting feature.
Supplementary materials are available at Clinical Infectious Diseases online.
Consisting of data provided by the authors to benefit the reader, the posted
materials are not copyedited and are the sole responsibility of the authors,
so questions or comments should be addressed to the corresponding author.
Financial support. This work was supported by research grants from
the US National Institute of Allergy and Infectious Diseases (NIAID) under
Centers of Excellence for Influenza Research and Surveillance contract
number HHSN272201400006C; and by the Research Grants Council of
the Hong Kong Special Administrative Region, China, through the
ThemeBased Research Scheme (grant number T11-705/14N to M. P.).
Potential conflicts of interest. All authors: No reported conflicts
of interest. All authors have submitted the ICMJE form for disclosure of
potential conflicts of interest. Conflicts that the editors consider relevant to
the content of the manuscript have been disclosed.
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