Human Bocavirus in Infants, New Zealand

In 2005, a parvovirus, subsequently named human bocavirus (HBoV), was discovered in respiratory samples taken from infants and children hospitalized at Karolinksa University Hospital, Sweden, with lower respiratory tract infection. HBoV has since been identified in infants and children with respiratory illness in >17 countries, at frequencies ranging from 1.5% to >18.0%. This study reaffirms previous reports of finding HBoV in a subset of infants with bronchiolitis. It is also, to our knowledge, the first study of its kind in New Zealand infants, confirming wide distribution of HBoV. In the northern hemisphere, HBoV circulates primarily during the winter months, although it continues circulating until early summer, later than most other seasonal respiratory viruses. Therefore, this study may underestimate the percentage of New Zealand infants with bronchiolitis whose HBoV test results were positive because sample collection ceased in October (southern hemisphere spring) at the end of the bronchiolitis epidemic. The small number of HBoV-positive infants prevents conclusions concerning ethnicity, coinfection, and bronchiolitis severity.


Human Bocavirus in Infants, New Zealand
To the Editor: In 2005, a parvovirus, subsequently named human bocavirus (HBoV), was discovered in respiratory samples taken from infants and children hospitalized at Karolinksa University Hospital, Sweden, with lower respiratory tract infection (1).HBoV has since been identifi ed in infants and children with respiratory illness in >17 countries, at frequencies ranging from 1.5% to >18.0%.
In the past decade New Zealand has experienced increasing bronchiolitis hospitalization rates, currently >70 admissions per 1,000 infants.To determine the contribution of HBoV to New Zealand's bronchiolitis disease prevalence, we tested samples collected from infants hospitalized with community-acquired bronchiolitis (2) during 3 consecutive winter epidemics (June to October, 2003; July to October, 2004; and June to October, 2005) in Wellington, NZ, for HBoV by PCR.The Central Regional Ethics Committee approved the study.Written, informed consent was obtained from the parent or guardian.
Demographic, clinical, and laboratory data were collected during hospitalization.Ethnicity of those who ascribe to >1 group was determined by using a national census method that prioritizes ethnicity as follows: Māori>Pacifi c>Other>New Zealand European.Oxygen requirement was determined to be the best measure of bronchiolitis severity (2).Infants who needed assisted ventilation or continuous positive airway pressure were classifi ed severe; those who required oxygen supplementation moderate; and infants who were hospitalized but did not require supplemental oxygen mild.
Eight (3.5%) of 230 samples, collected from infants hospitalized with bronchiolitis during the 2003-2005 winter epidemic seasons, were positive for HBoV.In 5 HBoV-positive infants no other pathogens were identifi ed, but RSV was detected in 3 (Table ).The 8 HBoV-positive infants had a median age of 9.5 months, and the male:female ratio was 1:1.The median length of hospital stay was 5.5 (range 1-16) days.
As expected, because HBoV NP-1 is highly conserved, sequence variation among New Zealand isolates and the prototype Stockholm ST-1 and ST-2 (1) NP-1 sequences was limited.Alignments of the partial NP-1 sequence (nt 2410-2602) of New Zea- land isolates with those of ST-1 and ST-2 were identical, except for a G→ A change at nt 176 in 2 New Zealand isolates (from infants 5 and 8 years of age), which resulted in a predicted amino acid exchange of S→N at aa 59.In addition, an A→T change at nt 274 in all 8 NZ isolates resulted in a predicted amino acid substitution of T→S at aa 92, a change that has been reported previously in Japanese isolates (6).

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This study reaffi rms previous reports of fi nding HBoV in a subset of infants with bronchiolitis (7).It is also, to our knowledge, the fi rst study of its kind in New Zealand infants, confi rming wide distribution of HBoV.In the northern hemisphere, HBoV circulates primarily during the winter months, although it continues circulating until early summer, later than most other seasonal respiratory viruses (8).Therefore, this study may underestimate the percentage of New Zealand infants with bronchiolitis whose HBoV test results were positive because sample collection ceased in October (south-ern hemisphere spring) at the end of the bronchiolitis epidemic.The small number of HBoV-positive infants prevents conclusions concerning ethnicity, coinfection, and bronchiolitis severity.
Although detection of viral nucleic acid by PCR in infants with bronchiolitis does not prove that the virus is the cause of the disease, it raises a hypothesis worthy of investigation.Further studies are required to determine the role of HBoV as a human pathogen.Although coinfection is common, HBoV detection appears to be infrequent in asymptomatic controls (9).In our study RSV was detected in 3 (37.5%)HBoV-positive samples.We may have underestimated additional coinfection because we did not test for several respiratory agents, including parainfl uenza viruses, rhinoviruses, or the newly discovered coronaviruses.
Finally, HBoV has recently been detected in fecal samples (10).Because 3 HBoV-positive infants had diarrhea in addition to bronchiolitis, knowing prevalence of HBoV in fecal specimens from asymptomatic New Zealand children and in those with acute gastroenteritis would be of interest.

Lyme Disease in Urban Areas, Chicago
To the Editor: Lyme disease is a multisystem illness caused by infection with the tickborne spirochete Borrelia burgdorferi.Most infections in the United States occur in the Northeast and upper Midwest, and the midwestern focus now includes Illinois (1,2).Previously, the greatest risk of contracting Lyme disease in the Midwest was confi ned to the northernmost states (Wisconsin and Minnesota) and did not encroach into heavily populated areas around the city of Chicago.However, we showed recently that B. burgdorferi-infected Ixodes scapularis ticks were recovered from sites in Cook and DuPage counties (3), but the percentages of infected ticks were low (<5%).Since that time, however, reports of Lyme disease in Cook County have been reviewed and individual I. scapularis tick submissions from Lake County, north of Chicago, have been received.We therefore surveyed new areas north of Chicago (closest was <1 mile from the city limits; farthest was ≈25 miles from the city limits) and examined additional ticks for infection with B. burgdorferi.
From December 2006 to May 2007, we collected 172 adult I. scapularis ticks from sites to the north and northwest of Chicago (Figure ).Adult ticks were collected because nymphal ticks are more diffi cult to obtain, and the infection rate in adult ticks is similar (1).The tick midguts were removed aseptically, inoculated into tubes containing 1 mL of modifi ed Barbour-Stoenner-Kelly medium (4), incubated at 35ºC, and examined for spirochetes for up to 3 weeks.Spirochetes were recovered from 21 (32%) of 65 ticks and 40 (37%) of 107 ticks collected from sites in Cook and Lake counties, respectively.In addition, PCR using primers specifi c for outer surface protein A (5) confi rmed that the spirochetes were B. burgdorferi.
The fi ndings demonstrate that the midwestern endemic focus of
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