RESUMO
OBJECTIVE: The frequency and seasonality of viruses in tropical regions are scarcely reported. We estimated the frequency of seven respiratory viruses and assessed seasonality of respiratory syncytial virus (RSV) and influenza viruses in a tropical city. METHODS: Children (age ≤ 18 years) with acute respiratory infection were investigated in Salvador, Brazil, between July 2014 and June 2017. Respiratory viruses were searched by direct immunofluorescence and real-time polymerase chain reaction for detection of RSV, influenza A virus, influenza B virus, adenovirus (ADV) and parainfluenza viruses (PIV) 1, 2 and 3. Seasonal distribution was evaluated by Prais-Winsten regression. Due to similar distribution, influenza A and influenza B viruses were grouped to analyse seasonality. RESULTS: The study group comprised 387 cases whose median (IQR) age was 26.4 (10.5-50.1) months. Respiratory viruses were detected in 106 (27.4%) cases. RSV (n = 76; 19.6%), influenza A virus (n = 11; 2.8%), influenza B virus (n = 7; 1.8%), ADV (n = 5; 1.3%), PIV 1 (n = 5; 1.3%), PIV 3 (n = 3; 0.8%) and PIV 2 (n = 1; 0.3%) were identified. Monthly count of RSV cases demonstrated seasonal distribution (b3 = 0.626; P = 0.003). More than half (42/76 [55.3%]) of all RSV cases were detected from April to June. Monthly count of influenza cases also showed seasonal distribution (b3 = -0.264; P = 0.032). Influenza cases peaked from November to January with 44.4% (8/18) of all influenza cases. CONCLUSIONS: RSV was the most frequently detected virus. RSV and influenza viruses showed seasonal distribution. These data may be useful to plan the best time to carry out prophylaxis and to increase the number of hospital beds.
Assuntos
Influenza Humana/epidemiologia , Infecções por Paramyxoviridae/epidemiologia , Infecções por Vírus Respiratório Sincicial/epidemiologia , Estações do Ano , Adenoviridae/isolamento & purificação , Brasil/epidemiologia , Pré-Escolar , Estudos Transversais , Feminino , Imunofluorescência , Humanos , Incidência , Lactente , Vírus da Influenza A/isolamento & purificação , Vírus da Influenza B/isolamento & purificação , Masculino , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Reação em Cadeia da Polimerase em Tempo Real , Vírus Sinciciais Respiratórios/isolamento & purificação , Clima TropicalRESUMO
PROBLEM: Human parainfluenza virus (hPIV) is an important pathogen in respiratory infections, however the health burden of hPIV is underestimated. This study describes the infections by hPIV1-3 in Rio Grande do Sul, Brazil, from 1990 to 2017, providing data of the frequency and seasonality of cases and associated clinical symptoms. METHOD OF STUDY: Nasopharyngeal samples of patients with respiratory infection were collected, clinical data were analyzed, and immunofluorescence was used to detect hPIV. RESULTS: Respiratory viruses were detected in 33.63% of respiratory infections. In a total of 11 606 cases of viral respiratory infection, 781 were positive for hPIV; hPIV prevalence ranged from 2.14% to 27% of viral respiratory infections. hPIV1 circulates mainly during fall; hPIV3 circulation, in turn, starts in fall and peaks during spring; and cases of hPIV2 are reported along the year, with peaks in fall and early spring. The most affected age group was children, with hPIV prevalence of 74.23% in patients for less than 1 year. A higher proportion of girls were infected than boys, however, no difference by sex was observed considering all age groups. The most frequent type was hPIV3, especially in hospitalized patients. Both hPIV1 and 3 were associated with dyspnea, while hPIV2 caused mild symptoms mainly in nonhospitalized patients. Nineteen fatalities occurred, 89.5% of them associated with risk factors (prematurity; chronic diseases; age, <1 or >60 years). CONCLUSION: hPIV causes a high number of respiratory infections, leading to hospitalization especially in children; epidemiological and surveillance studies are important for the control and management of respiratory infections.
Assuntos
Infecções por Paramyxoviridae/epidemiologia , Infecções Respiratórias/epidemiologia , Adolescente , Adulto , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Brasil/epidemiologia , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Nasofaringe/virologia , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Prevalência , Infecções Respiratórias/virologia , Estações do Ano , Distribuição por Sexo , Adulto JovemRESUMO
Acute respiratory infections are responsible for high morbi-mortality in Peruvian children. However, the etiological agents are poorly identified. This study, conducted during the pandemic outbreak of H1N1 influenza in 2009, aims to determine the main etiological agents responsible for acute respiratory infections in children from Lima, Peru. Nasopharyngeal swabs collected from 717 children with acute respiratory infections between January 2009 and December 2010 were analyzed by multiplex RT-PCR for 13 respiratory viruses: influenza A, B, and C virus; parainfluenza virus (PIV) 1, 2, 3, and 4; and human respiratory syncytial virus (RSV) A and B, among others. Samples were also tested with direct fluorescent-antibodies (DFA) for six respiratory viruses. RT-PCR and DFA detected respiratory viruses in 240 (33.5%) and 85 (11.9%) cases, respectively. The most common etiological agents were RSV-A (15.3%), followed by influenza A (4.6%), PIV-1 (3.6%), and PIV-2 (1.8%). The viruses identified by DFA corresponded to RSV (5.9%) and influenza A (1.8%). Therefore, respiratory syncytial viruses (RSV) were found to be the most common etiology of acute respiratory infections. The authors suggest that active surveillance be conducted to identify the causative agents and improve clinical management, especially in the context of possible circulation of pandemic viruses.
Assuntos
Vírus da Influenza A/isolamento & purificação , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus Sincicial Respiratório Humano/isolamento & purificação , Infecções Respiratórias/epidemiologia , Infecções Respiratórias/virologia , Doença Aguda , Criança , Feminino , Técnica Direta de Fluorescência para Anticorpo , Humanos , Incidência , Lactente , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Influenza Humana/epidemiologia , Masculino , Reação em Cadeia da Polimerase Multiplex , Nasofaringe/virologia , Peru/epidemiologia , Infecções por Vírus Respiratório Sincicial/epidemiologia , Infecções por Respirovirus/epidemiologia , Infecções por Rubulavirus/epidemiologia , Fatores de TempoRESUMO
Respiratory viral infections are frequent causes of morbidity in transplant patients. We screened symptomatic adult transplant recipients for respiratory viruses in a cohort of patients attending a referral medical center in Brazil. The duration of viral shedding and the prevalence of viral codetections were also determined. During a 1-year period (2011-2012), swabs were obtained from 50 patients. An in-house polymerase chain reaction panel designed to detect 10 viruses was used. Viruses were identified in 19 (38%) patients, particularly parainfluenza III (32%) and the respiratory syncytial virus (20%); multiple viruses were identified in 26% of patients. Prolonged viral shedding was observed with 60% of individuals excreting viruses for >10 days. The clinical and epidemiologic relevance of prolonged viral shedding remains to be determined.
Assuntos
Rejeição de Enxerto/prevenção & controle , Hospedeiro Imunocomprometido , Imunossupressores/uso terapêutico , Transplante de Órgãos , Infecções Respiratórias/transmissão , Viroses/transmissão , Eliminação de Partículas Virais , Adulto , Idoso , Estudos de Coortes , Coinfecção , Feminino , Humanos , Vírus da Influenza A/genética , Vírus da Influenza B/genética , Influenza Humana/imunologia , Influenza Humana/transmissão , Transplante de Rim , Transplante de Fígado , Transplante de Pulmão , Masculino , Pessoa de Meia-Idade , Vírus da Parainfluenza 1 Humana/genética , Vírus da Parainfluenza 2 Humana/genética , Vírus da Parainfluenza 3 Humana/genética , Estudos Prospectivos , Reação em Cadeia da Polimerase em Tempo Real , Infecções por Vírus Respiratório Sincicial/imunologia , Infecções por Vírus Respiratório Sincicial/transmissão , Vírus Sinciciais Respiratórios/genética , Infecções Respiratórias/imunologia , Infecções Respiratórias/virologia , Infecções por Respirovirus/imunologia , Infecções por Respirovirus/transmissão , Fatores de Tempo , Viroses/imunologia , Viroses/virologia , Adulto JovemRESUMO
Little information on the epidemiology and clinical characteristics of human parainfluenza virus (HPIV) infections, especially in children from tropical countries, has been published. The aim of this study was to determine the frequency of HPIV infections in children attended at a large hospital in Fortaleza in Northeast Brazil, and describe seasonal patterns, clinical and epidemiological characteristics of these infections. From January 2001 to December 2006, a total of 3070 nasopharyngeal aspirates collected from children were screened by indirect immunofluorescence for human parainfluenza viruses 1, 2, and 3 (HPIV-1, 2 and 3) and other respiratory viruses. Viral antigens were identified in 933 samples and HPIV in 117. The frequency of HPIV-3, HPIV-1 and HPIV-2 was of 83.76%, 11.96% and 4.27%, respectively. Only HPIV-3 showed a seasonal occurrence, with most cases observed from September to November, and with an inverse relationship to the rainy season. Most HPIV-3 infections seen in outpatients were diagnosed as upper respiratory tract infections.
Assuntos
Infecções Respiratórias/epidemiologia , Infecções Respiratórias/virologia , Adenoviridae/isolamento & purificação , Adolescente , Brasil/epidemiologia , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Recém-Nascido , Vírus da Influenza A/isolamento & purificação , Masculino , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus Sinciciais Respiratórios/isolamento & purificação , Infecções Respiratórias/diagnóstico , Respirovirus/isolamento & purificação , Estações do AnoRESUMO
BACKGROUND: Human parainfluenza viruses (hPIV) are a common cause of respiratory illness of children but published data on clinical characteristics of hPIV infection in South America is scarce. OBJECTIVE: To review the clinical presentation and epidemiological features of hPIV in a series of hospitalized children in Chile. PATIENTS AND METHODS: Retrospective review of clinical charts from all pediatric admissions with a diagnosis of respiratory disease (between January 2001 to December 2004) at the Catholic University Hospital, Santiago, Chile. Nasopharyngeal secretions were tested for hPIV in children admitted with suspected respiratory viral infections. RESULTS: A total of 3,043 respiratory admissions were recorded during the study period; 64 children (2.1%) were hPIV positive. Average age was 13 months (range: lm to 12y) and 77%> were younger than 2 years. HPIV-2 was the most common type identified (47%). A seasonal trend was noted for serotypes hPIV-2 and 3. Acute wheezing (40%o) and pneumonia (30%) were the most common clinical diagnosis in hPIV positive children and 17%> hPIV positive children (44%> for hPIV-1) were associated with laryngitis. All hPIV positive bronchiolitis were due to serotypes hPIV-2 and 3. CONCLUSION: hPIV can cause respiratory disease requiring hospitalization; serotypes hPIV-2 and 3 displayed a seasonal trend. Although hPIV is an uncommon cause of severe respiratory infecion requiring hospitalization in children, it should be considered in the differential diagnosis of laryngitis, bronchiolitis and pneumonia, especially in younger children.
Assuntos
Hospitalização/estatística & dados numéricos , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Infecções por Respirovirus/epidemiologia , Infecções por Rubulavirus/epidemiologia , Criança , Pré-Escolar , Chile/epidemiologia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Infecções por Respirovirus/diagnóstico , Infecções por Respirovirus/virologia , Estudos Retrospectivos , Infecções por Rubulavirus/diagnóstico , Infecções por Rubulavirus/virologia , Estações do Ano , SorotipagemRESUMO
Se estudió la presencia de anticuerpos contra los virus Parainfluenza humanos tipos 2 y 3 en 1 793 sueros de una población infantil menor de 14 años de edad. Para el pesquisaje de las muestras clínicas se empleó como sistema la técnica de inhibición de la hemaglutinación. Del total de sueros analizados fueron positivos 1 382 (77,1 por ciento), de estos se confirmó la presencia de anticuerpos contra el tipo 2 en 320 (17,8 por ciento), para el tipo 3 en 334 (18,6 por ciento) y predominó la seropositividad simultánea en 805 (44,9 por ciento). Se constató la circulación de los virus Parainfluenza humanos durante todos los meses del año y en todos los grupos de edades analizados, con aumento en los porcentajes de positividad con la edad
Assuntos
Humanos , Criança , Hemaglutinação por Vírus , Vírus da Parainfluenza 2 Humana , Vírus da Parainfluenza 3 HumanaRESUMO
The presence of antibodies against human parainfluenza viruses type 2 and 3 was studied in 1 793 sera from an infantile population under 14 years old. The hemagglutination inhibition technique was used for screening the clinical samples. Of the total of analyzed sera, 1 382 (77.1%) were positive. The presence of antibodies against type 2 was confirmed in 320 of them (17.8%), and against type 3 in 334 (18.6%). The simultaneous seropositivity predominated in 805 (44.9%). The circulation of human parainfluenza viruses was corroborated during all the months of the year and in all the analyzed age groups. It was observed an increase in the positivity percentages with age.
Assuntos
Crupe/epidemiologia , Laringite/epidemiologia , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Traqueíte/epidemiologia , Adolescente , Fatores Etários , Anticorpos Antivirais/análise , Criança , Pré-Escolar , Crupe/virologia , Cuba/epidemiologia , Testes de Inibição da Hemaglutinação , Humanos , Lactente , Recém-Nascido , Laringite/virologia , Vírus da Parainfluenza 2 Humana/imunologia , Vírus da Parainfluenza 3 Humana/imunologia , Vigilância da População , Estudos Retrospectivos , Estações do Ano , Estudos Soroepidemiológicos , Traqueíte/virologiaRESUMO
BACKGROUND: Viral upper respiratory tract infections (URTI) have been correlated with the onset of asthma attacks in children and viral identification was reported in 14-49 % of nasal samples. The aim of the present study was to detect influenza, parainfluenza, adenovirus and respiratory syncytial virus (RSV) in older children during acute asthma attacks. METHODS: A total of 104 children (2-14 years) were included in four groups: group I: asthmatics with acute attack and URTI; group II: asthmatics without URTI (group I children, 30 days later); group III: non-asthmatics with URTI; group IV: non-asthmatic, asymptomatic children. A diagnosis of URTI was considered when (3 symptoms (cough and/or sneeze, nasal obstruction, hypertrophy of turbinates, pain and/or retropharynx hyperemia, headache and fever) in asthmatics and at least 2 symptoms in non-asthmatics were present, starting within 7 days. Samples of nasal mucosa cells (n = 123) were collected, and culture and indirect immunofluorescence were carried out to identify respiratory syncytial virus, adenovirus, influenza A and B, parainfluenza 1,2 and 3 and rhinovirus. RESULTS: Viral identification rates were higher in the asthmatic groups: 13.9 % in group I, 11.1 % in group II; 2.8 % in group III and 0 in group IV. The following viruses were identified: RSV 2/36, rhinovirus 1/36, adenovirus 1/36 and parainfluenzae 1/36 in group I; adenovirus 2/18 in group II; RSV 1/36 in group III. CONCLUSIONS: The rate of viral identification was higher in asthmatic children, whether symptomatic or not, suggesting a possible susceptibility to viral infections. Virus could also be a triggering factor in attacks, although it is not the most preponderant in older children.
Assuntos
Asma/epidemiologia , Infecções Respiratórias/epidemiologia , Viroses/epidemiologia , Infecções por Adenovirus Humanos/epidemiologia , Adenovírus Humanos/isolamento & purificação , Adolescente , Asma/virologia , Brasil/epidemiologia , Criança , Pré-Escolar , Suscetibilidade a Doenças , Feminino , Humanos , Hipersensibilidade Imediata/epidemiologia , Vírus da Influenza A/isolamento & purificação , Vírus da Influenza B/isolamento & purificação , Influenza Humana/epidemiologia , Masculino , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Infecções por Paramyxoviridae/epidemiologia , Infecções por Paramyxoviridae/virologia , Hipersensibilidade Respiratória/epidemiologia , Infecções por Vírus Respiratório Sincicial/epidemiologia , Vírus Sincicial Respiratório Humano/isolamento & purificação , Infecções Respiratórias/virologia , Estações do Ano , Viroses/virologiaRESUMO
La laringotraqueobronquitis o crup viral es una de las entidades clínicas más frecuentes y clásicas de la patología respiratoria pediátrica. La presente revisión evalúa, a la luz de las más recientes publicaciones sobre el tema, el papel terapéutico de medidas como la aerosolterapia, las nebulizaciones de epinefrina racémica, adrenalina y fenilefrina, la administración parenteral de glucocorticoides y el empleo de una escala de puntaje para evaluar la severidad del compromiso del paciente y la respuesta al tratamiento.
Assuntos
Humanos , Pré-Escolar , Criança , Crupe , Vírus da Parainfluenza 2 Humana/classificação , Vírus da Parainfluenza 2 Humana/patogenicidade , Vírus da Parainfluenza 2 Humana/fisiologia , Vírus da Parainfluenza 2 Humana/classificação , Vírus da Parainfluenza 2 Humana/patogenicidadeRESUMO
Las enfermedaes respiratorias infantiles constituyen la causa más frecuente de consulta al pediatra. Las características anatómicas de la vía aérea, la predisposición alérgica y las condiciones epidemiológicas hacen al niño más vulnerable al contagio con agentes virales. La laringotraqueobronquitis es una enfermedad de etiología viral y su curso normal dura aproximadamente una semana, descartando el tratamiento antibióticvo, en la mayoría de los casos. La evaluación médica es el método de disgnóstico más importante. Las medidas generales de tratamiento, como ambiente tranquilo, estímulos mínimos y reducción de estrés y dolor, son factores que favorecen la regresión espontánea de la obstrucción de la vía aérea
Assuntos
Humanos , Criança , Crupe/terapia , Vírus da Parainfluenza 2 Humana/patogenicidade , Corticosteroides/uso terapêutico , Crupe/diagnóstico , Crupe/etiologia , Crupe/fisiopatologia , Diagnóstico Diferencial , Índice de Gravidade de DoençaRESUMO
Os autores, com base na experiência pessoal e na literatura, apresentam como se conduzem nos casos de LTB, principalmente nos graves. Abordam a incidência, etiologia, diagnóstico, tratamento e indicaçöes para intubaçäo, bem como os mecanismos de defesa do pulmäo
Assuntos
Humanos , Masculino , Feminino , Lactente , Brônquios , Endoscopia , Infecções Respiratórias/etiologia , Intubação Intratraqueal/métodos , Laringe , Traqueia , Diagnóstico Diferencial , Infecções Respiratórias/diagnóstico , Infecções Respiratórias/epidemiologia , Infecções Respiratórias/etiologia , Vírus da Parainfluenza 2 Humana , Pulmão/fisiologia , Pulmão/imunologiaRESUMO
El presente estudio fué realizado en el Departamento de Pediatria del Hospital Materno Infantil Germán Urquidi, habiendose revisado 50 historias clinicas que son el total de pacientes que egresaron con diagnóstico de laringotraqueobronquitis aguda durante el periodo de 1988 hasta Diciembre de 1990. Los resultados mas relevantes son el hecho de que la mayor incidencia corresponde a los meses de Mayo, Junio y Agosto con 18, 12 por ciento y 14 por ciento respectivamente. Es patologia de Eutróficos y desnutridos de primer grado en un 82 por ciento; el 52 por ciento de los casos se presentan en horario nocturno y el tratamiento mas usado es el esquema de vapor mas oxigeno antibioticos y cortocosteroides, en las difunciones fue por cardiopatia congénita asociada y otros por complicación séptica y encefalopatia hipoxica. En un solo caso fue necesario la traqueostomía con resultado favorable posterior y otro aquien se entubo por periodos de apnéa prolongada y daño hipoxico manifiesto ya desde su ingreso, quien fallecio posteriormente, el tiempo promedio de internación fue de 3 dias.
Assuntos
Humanos , Masculino , Feminino , Lactente , Pré-Escolar , Doenças da Laringe/complicações , Doenças da Laringe/diagnóstico , Vírus da Parainfluenza 2 Humana , Estudos Transversais , Estudos Retrospectivos , Epidemiologia DescritivaRESUMO
Los virus respiratorios se detectan en un alto porcentaje en la patología respiratoria aguda que afecta al lactante. No nos debe llamar la atención que un alto porcentaje de virus detectados aparecieron en los cuadros de Neumonitis. Es llamativo el alto porcentaje de positividad viral encontrado en las Bronconeumonias. Por último, el aumento de la detección viral observada en los últimos años se debe fundamentalmente a la introducción de nuevas técnicas, específicamente, la detección de antígenos virales por inmunofluorescencia directa y aislamiento viral a partir del aspirado nasofaríngeo y también, a la adecuada toma, envío y procesamiento de las muestras
Assuntos
Lactente , Humanos , Infecções Respiratórias/diagnóstico , Adenovírus Humanos/isolamento & purificação , Vírus da Parainfluenza 1 Humana/isolamento & purificação , Vírus da Parainfluenza 2 Humana/isolamento & purificação , Vírus da Parainfluenza 3 Humana/isolamento & purificação , Vírus Sinciciais Respiratórios/isolamento & purificação , Testes de Fixação de Complemento/métodos , Testes de Inibição da Hemaglutinação/métodosRESUMO
In order to determine the role of parainfluenza virus-specific IgE antibody production and release of histamine in the pathogenesis of lower respiratory disease caused by parainfluenza virus infection, we studied 84 infants and children at the time of parainfluenza virus infection. Parainfluenza virus-IgE antibody was detected in samples of nasopharyngeal secretions by means of an enzyme-linked immunosorbent assay, and histamine content of nasopharyngeal secretions was determined by a fluorometric technique. Virus-specific IgE responses appeared earlier and were of greater magnitude in patients with croup, wheezing, and croup with wheezing caused by parainfluenza virus infection than in patients with parainfluenza virus-induced upper respiratory illness. Histamine was detectable in nasopharyngeal secretions of patients with parainfluenza virus-related croup significantly more often than in patients with upper respiratory illness caused by parainfluenza virus. These observations suggest a role for immunologic mechanisms in the pathogenesis of severe forms of respiratory illness caused by parainfluenza virus infection.
Assuntos
Anticorpos Antivirais/biossíntese , Crupe/imunologia , Imunoglobulina E/imunologia , Laringite/imunologia , Vírus da Parainfluenza 2 Humana/imunologia , Sons Respiratórios/imunologia , Infecções Respiratórias/imunologia , Respirovirus/imunologia , Pré-Escolar , Crupe/etiologia , Liberação de Histamina , Humanos , Lactente , Mucosa Nasal/metabolismo , Respiração , Sons Respiratórios/etiologia , Infecções Respiratórias/complicaçõesRESUMO
In order to determine the natural history of parainfluenza virus infection in early life, we followed prospectively 130 infants and children from birth or a few months of age for evidence of infection with PV. Using rapid diagnostic techniques, standard tissue culture infectivity, and serologic techniques we were able to document primary PV infection in 92% of these infants, and repeated infection with heterotypic or homotypic PV strains in 49% by 30 months of age. Increasing patient age had no significant effect in reducing the incidence of lower respiratory tract illness as a result of PV infection. Infection with one PV serotype provided no protection against LRTI at the time of subsequent infection with a heterotypic PV strain. In contrast, primary PV infection provided a brief period of immunity to LRTI upon homotypic reinfection. Secretory IgA responses to PV were determined by immunofluorescent techniques. Antibody response to PV strains causing primary infection and heterotypic repeated infection were transient and of low magnitude. Homotypic reinfection resulted in significantly enhanced production of secretory antibody to PV. At least in early life, repeated exposures to PV appear to be essential for maintaining immunity to severe forms of illness caused by PV infection.