Barbara D. Baxter

Dual Respiratory Virus Infections

Abstract We retrospectively reviewed eight prospective epidemiological studies conducted between 1991 and 1995 for dual respiratory virus infection (DRVI) to determine the frequency, associated comorbid conditions, clinical presentations, and morbidity related to DRVI among immunocompetent persons. Two viruses were identified as the cause of 67 (5.0%) of 1,341 acute respiratory virus infections. DRVI was detected in patients from <1 year to 79 years of age, in both sexes, and in many races. Forty-two percent of patients with DRVI were ⩽4 years old. Fifty-eight percent of patients with DRVI had underlying chronic lung disease. DRVI was associated with upper respiratory tract illness; lower respiratory tract illness, including pneumonia; systemic influenza-like illnesses; and exacerbations of asthma or chronic obstructive pulmonary disease. All of the common acute respiratory viruses were identified; picornaviruses and influenzavirus A were the most common. The rate of DRVI (11.6%) was highest in the epidemiological studies in which cell culture, serology, and polymerase chain reaction were used together. Patients with DRVI were hospitalized significantly more often than those with respiratory infection due to a single virus (46.3% vs. 21.7%; P < .01). The percentage of DRVIs increased proportionally with the number of diagnostic methods used.

Influenza A virus outbreak in a neonatal intensive care unit.

BACKGROUND Nosocomial infections with influenza virus are rarely recognized in neonatal intensive care units (NICU). An outbreak of influenza A virus infection in the NICU of an urban county hospital during the 1997 to 1998 influenza season is reported. METHODS Clinical and virologic data were recorded in all symptomatic NICU patients after influenza A infection was diagnosed in one infant in October, 1997. RESULTS Influenza A/H3N2 was isolated from two of four symptomatic infants. The application of rapid diagnostic techniques for the characterization of influenza virus infection allowed the timely institution of basic infection control measures, limiting this outbreak. Resistance to amantadine was documented for the first time in this patient population by reverse transcription-PCR within 48 h of treatment in one case. CONCLUSIONS Prevention by immunization is a priority in those caring for high risk NICU patients.

Studies on reactogenicity and immunogenicity of attenuated bivalent cold recombinant influenza type A (CRA) and inactivated trivalent influenza virus (TI) vaccines in infants and young children

Fifty-two infants seronegative to or without prior infection with influenza type A viruses were enrolled in a study to evaluate reactogenicity and immunogenicity of three bivalent cold recombinant type A (CRA) and two trivalent inactivated influenza (TI) vaccines. Controls consisted of infants receiving normal saline by nose drops (Pli.n.) or intramuscularly (Pli.m.). CRA and TI vaccines were monitored for local and systemic reactions after vaccination. Serum specimens obtained prior to and 6 weeks postvaccination were analysed for neutralizing antibody to influenza H1N1 and H3N2 viruses. CRA vaccines and Pli.n. recipients had similar numbers of acute respiratory infections and comparable rates of illnesses during the trial. Significantly fewer CRA vaccinees without an intercurrent viral infection had fever (0/16 versus 4/10, p = 0.04) and cough (4/16 versus 9/10, p = 0.002) than CRA vaccinees with a confirmed intercurrent viral infection. Recipients of TI vaccine and Pli.m. did not develop reactions at the injection site. For each of the CRA vaccines tested, a dominant CRA virus was identified. The dominant CRA viruses were isolated from a greater number of infants or for a longer duration than the non-dominant CRA viruses. All 14 non-dominant CRA viruses were recovered from infants within the first week after vaccination; 24 of 77 dominant CRA viruses were recovered more than 7 days after vaccination. The immunogenicity of CRA vaccines was not affected by a confirmed intercurrent viral infection or low titres of influenza-specific antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Typing and subtyping clinical isolates of influenza virus using reverse transcription-polymerase chain reaction

BACKGROUND Influenza virus infections are a major cause of morbidity and the identification of the type or subtype of a clinical isolate has important clinical and epidemiological implications. OBJECTIVES To evaluate the ability of a reverse transcription-polymerase chain reaction (RT-PCR) assay to type and subtype clinical human isolates of influenza virus. STUDY DESIGN Reference strains of influenza A H1N1, A/H3N2, and B viruses and human clinical isolates of influenza virus representing antigenic variants from the last 15 years were evaluated using an RT-PCR assay. RESULTS Amplicons of 325, 198 and 365 base pairs in length were obtained from RNA extracted from influenza A/H1N1, A/H3N2 and B viruses, respectively. All human-derived A/H1N1, A/H3N2, and B reference strains and antigenic variants tested were correctly identified. CONCLUSIONS RT-PCR is an effective alternative to traditional methods for typing and subtyping influenza viruses.