Assessing the heterogeneity of disease spread through a community.

Care needs to be exercised in attempts at obtaining a description of the spread of disease merely by fitting a mathematical model to infectious disease data and adjusting the model until it adequately fits the observed epidemic curve. It is always necessary to perform separate statistical tests of the underlying assumptions of an epidemic model before attempting to use such a model to obtain epidemiologically meaningful insights into the mechanism of disease spread. Methods for such tests are presented and illustrated with reference to epidemics of respiratory diseases that occurred on the island of Tristan da Cunha in the South Atlantic between 1964 and 1968.

Concurrent outbreaks of rhinovirus and respiratory syncytial virus in an intensive care nursery: epidemiology and associated risk factors.

An outbreak of viral respiratory disease occurred in eight infants in a neonatal intensive care unit during the 1980 winter respiratory season. Four infections with respiratory syncytial virus and four infections with rhinovirus were identified. Epidemiologic investigation revealed that viral respiratory infection was significantly associated with intubation with orotracheal tubes (P = 0.001), with the presence of both a nasal feeding tube plus an orotracheal tube together (P = 0.007), and with assisted ventilation (P = 0.009) when compared to uninfected controls. Twenty-seven of 85 (30.6%) personnel working in the unit at the time of the outbreak reported a history of upper respiratory illness during the week prior to the outbreak, and 46 (54.1%) of them had had contact with patients in areas of the hospital where patients infected with RSV and rhinovirus were housed. The data suggest that both viruses were transmitted to the babies by hospital personnel. Rhinoviruses can be nosocomial pathogen in neonates with compromised pulmonary function, and the clinical presentation of rhinovirus infection in neonates may be difficult to distinguish from that produced by RSV.

Family-acquired respiratory disease in high-risk infants.

Five infants who had been patients in the same Neonatal Intensive Care Unit (NICU) were readmitted with respiratory illness. The illness was characterized by cough, congestion, apnea, and infiltration of the lungs revealed by radiographic examination. Only one infant was febrile. All five patients recovered; however, one infant required prolonged intubation and mechanically assisted ventilation. Investigation revealed that the illness was associated with prematurity and contact with ill family members. Illness was not associated with exposure to ill personnel in the NICU, low birth weight, or previous lung disease. This outbreak demonstrates the dangers involved in sending premature infants home when respiratory illness is prevalent in the family.

Relationship of microbial indicators to health effects at marine bathing beaches.

Findings are described from the second year of an epidemiological-microbiological study conducted at New York City beaches as part of the U.S. Environmental Protection Agency program to develop health effects-recreational water quality criteria. Symptomatology rates among swimmers (defined as immersion of the head in the water) relative to nonswimming but beach-going controls at a "barely acceptable" (BA) beach and a "relatively unpolluted" (RU) beach were examined. Data were collected by contacting family groups at the beach on weekends, obtaining information on bathing activity, and then questioning them by phone some 8--10 days later. In addition measurements were made for a number of potential water quality indicators. It was observed that the symptom rates, categorized as gastrointestinal (GI), respiratory, "other", and "disabling" (stayed home, stayed in bed, consulted a physician), were higher among swimmers than nonswimmers. As in the pretest conducted the previous year, the rate of GI symptoms was significantly higher among swimmers relative to nonswimmers at the BA but not the RU beach. Children, Hispanic Americans, and the low-middle socioeconomic groups were identified as the most susceptible portions of the population.

Transmission of acute respiratory disease (rhinotracheitis) of turkeys.

Clinical signs of acute respiratory disease of turkeys were transmitted to susceptible day-old poults by direct contact, litter contact, and drinking water. Attempts failed to transmit the disease by air (cage-to-cage) or by oral and nasal inoculation with feces, nasal exudates, or nasal turbinate extracts. The disease was not transmitted by inoculation with white blood cells. Chicks were not affected by the disease, but young quail developed signs of respiratory disease when exposed to contaminated drinking water. Thus, acute respiratory disease in turkeys appears to be of an infectious nature, and the infectious agent(s) probably exist in the heavily contaminated environment used to house young commercial turkey poults.

A study of acute respiratory disease in the community of Port Chalmers. II. Influenza A/Port Chalmers/1/73: intrafamilial spread and the effect of antibodies to the surface antigens.

During the first year of a study of respiratory disease in the semi-isolated community of Port Chalmers, New Zealand, an epidemic of clinical influenza occurred from which the variant influenza A/Port Chalmers/1/73 (H3N2) was isolated. Within a selected group of 26 families, 59 (46%) members had clinical or laboratory evidence of infection. During intrafamilial spread the infection frequency was highest for school-aged children (77%), followed by female adults (67%), infants (64%) and male adults (41%). The index infection in each family was a school-age child on 10 occasions, suggesting the role of this age group in the transmission of influenza A in this community. The secondary attack rate (SAR) of 58.3% was higher than expected. In sera taken before the 1973 epidemic, 59% of family members had detectable HI antibody and 25% NI antibody to A/England/42/72 while 38% had detectable HI antibody and 8% NI antibody to A/Port Chalmers/1/73. The relation between pre-existing antibody and infection frequency is discussed.