Scott F. Dowell

We conducted a household survey among Sa Kaeo residents to characterize self-reported health-seeking behavior for pneumonia and the proportion of individuals who seek care at a hospital to determine the coverage of a surveillance system. A 2-stage cluster sample was used to select households. A case of pneumonia was defined as a self-reported history of cough and difficulty breathing for at least 2 days or being given a diagnosis of pneumonia by a healthcare provider in the 12-month period beginning February 1, 2002, and ending January 31, 2003. Interviewers administered a structured questionnaire that asked about clinical illness and utilization of healthcare services. Among 1,600 households, 5,658 persons were surveyed, of whom 62 persons met the case definition. Of the 59 persons with complete data, 53 (90%, 95% CI: 79-96) sought medical care and 47 (80%, 95% CI: 67-89) sought care at a hospital facility in the province. Neither distance nor cost was reported as a barrier to seeking care. Most individuals with self-reported pneumonia sought care at the hospital level. Population-based surveillance can provide reliable estimates of hospitalized, chest radiograph-confirmed pneumonia in Sa Kaeo if adjustments are made to account for the proportion of individuals who access a hospital where radiologic assessment is available.

Pandemic influenza arrived in Iceland on October 19, 1918, and spread across the country with a speed and virulence that was typical of the so-called Spanish flu. The epidemiologic features of this pandemic are described by Gottfredsson et al. (1) in this issue of PNAS. These features, only now being described with precision some 90 years after the events, help to explain the unusual lethality of the historical epidemic and also highlight vulnerabilities that might be exploited for modern control measures. However, the most important contribution of the Gottfredsson et al. article is the detailed analysis of genetic susceptibility and their conclusion that family exposures outweighed genetics as risk factors for fatal influenza during this pandemic. This finding was made possible both because of the unique genealogical database that exists in Iceland and because the rapid spread of the disease across the island enabled the authors to identify pandemic deaths with relative precision. The 1918 pandemic of influenza moved across Iceland in only 42 days, a phenomenon more influenced by the very short serial interval of 4.1 days between generations of cases than by the transmissibility of the virus. Transmissibility, measured as the average number of individuals infected by each case, was modest at 2.2 for the Iceland epidemic, and mortality was 2.8% with a W-shaped age distribution curve. This is consistent with estimates from other countries (2–5) that have prompted speculation that similar viruses might be vulnerable to early containment (2, 6). During those 42 days, 521 Icelanders died, an increase of >500% from the comparable period of the year before. This unprecedented clustering of deaths in a short period also allowed the investigators to identify influenza-associated deaths with unusual precision, despite the lack of a specific diagnostic test in the previral era. Specificity in the …

Little is known about the disease burden of influenza in middle-income tropical countries like Thailand. The recent outbreak of avian influenza (H5N1) and studies on influenza from neighboring countries highlight the need for data on incidence, access to care, and health care cost. In May/ June 2003, we conducted a province-wide household survey using two-stage cluster sampling to determine the burden of influenza-like illness in Sa Kaeo Province. We used the total number of reported influenza that occurred in May 2003 and a prospective study of outpatient influenza in clinic patients to develop an estimate of the annualized incidence of influenza. Of 718 subjects, 16 (2.2%) suffered an episode of influenza-like illness in the preceding month; 14 sought care, of whom 7 went to a hospital facility. Fifty percent reported missing on average 3 days of work or school. The total individual cost per illness episode was 663 baht (15.78 US dollars). The proportion of outpatients with influenza-like illness caused by an influenza virus in May was 16% and the annualized influenza incidence was estimated to be 5,941/100,000 in Sa Kaeo Province. This survey adds to information indicating that in rural Thailand, the burden of influenza is substantial and costs associated with an illness episode are up to 20% of an average monthly income.

Influenza A (H5N1) is endemic in poultry across much of Southeast Asia, but limited information exists on the distinctive features of the few human cases. In Thailand, we instituted nationwide surveillance and tested respiratory specimens by polymerase chain reaction and viral isolation. From January 1 to March 31, 2004, we reviewed 610 reports and identified 12 confirmed and 21 suspected cases. All 12 confirmed case-patients resided in villages that experienced abnormal chicken deaths, 9 lived in households whose backyard chickens died, and 8 reported direct contact with dead chickens. Seven were children <14 years of age. Fever preceded dyspnea by a median of 5 days, and lymphopenia significantly predicted acute respiratory distress syndrome development and death. Among hundreds of thousands of potential human cases of influenza A (H5N1) in Asia, a history of direct contact with sick poultry, young age, pneumonia and lymphopenia, and progression to acute respiratory distress syndrome should prompt specific laboratory testing for H5 influenza.

On March 11, 2003, a World Health Organization (WHO) physician was admitted to Bamrasnaradura Institute, after alerting the world to the dangers of severe acute respiratory syndrome (SARS) in Vietnam and developing a fever himself. Specimens from the first day of his admission were among the first to demonstrate the novel coronavirus, by culture, reverse transcription-polymerase chain reaction (RT-PCR), and rising of specific antibody, but proper protective measures remained unknown. The authors instituted airborne, droplet and contact precautions from the time of admission, and reviewed the efficacy of these measures. A specific unit was set up to care for the physician, beginning by roping off an isolated room and using a window fan to create negative pressure, and later by constructing a glass-walled antechamber, designated changing and decontamination areas, and adding high-efficiency particulate air (HEPA) filters. The use of personal protective equipment (PPE) was consistently enforced by nurse managers for all the staff and visitors, including a minimum of N95 respirators, goggles or face shields, double gowns, double gloves, full head and shoe covering, and full Powered Air Purifying Respirator (PAPR) for intubation. To assess the adherence to PPE and the possibility of transmission to exposed staff a structured questionnaire was administered and serum samples tested for SARS coronavirus by enzyme-linked immunosorbent assay (ELISA). Exposure was defined as presence on the SARS ward or contact with laboratory specimens, and close contact was presence in the patient's room. The WHO physician died from respiratory failure on day 19. 112 of 129 exposed staff completed questionnaires, and the 70 who entered the patient's room reported a mean of 42 minutes of exposure (range 6 minutes-23.5 hours). 100% reported consistent handwashing after exposure, 95% consistently used a fit-tested N95 or greater respirator, and 80% were fully compliant with strict institutional PPE protocol. No staff developed an illness consistent with SARS. Serum samples from 35 close contacts obtained after day 28 had a negative result for SARS coronavirus antibody. Hospitalization of one of the earliest SARS patients with documented coronavirus shedding provided multiple opportunities for spread to the hospital staff, but strict enforcement of conservative infection control recommendations throughout the hospitalization was associated with no transmission.

As of April 14, 2003, Taiwan had had 23 probable cases of severe acute respiratory syndrome (SARS), all imported. Taiwan isolated these first 23 patients with probable SARS in negative-pressure rooms; extensive personal protective equipment was used for healthcare workers and visitors. For the first 6 weeks of the SARS outbreak, recognized spread was limited to one healthcare worker and three household contacts.

Pneumococcal infections increase each winter, a phenomenon that has not been well explained. We conducted population-based active surveillance for all cases of invasive pneumococcal disease in seven states; plotted annualized weekly rates by geographic location, age, and latitude; and assessed correlations by time-series analysis. In all geographic areas, invasive pneumococcal disease exhibited a distinct winter seasonality, including an increase among children in the fall preceding that for adults and a sharp spike in incidence among adults each year between December 24 and January 7. Pneumococcal disease correlated inversely with temperature (r –0.82 with a 1-week lag; p<0.0001), but paradoxically the coldest states had the lowest rates, and no threshold temperature could be identified. The pattern of disease correlated directly with the sinusoidal variations in photoperiod (r +0.85 with a 5-week lag; p<0.0001). Seemingly unrelated seasonal phenomena were also somewhat correlated. The reproducible seasonal patterns in varied geographic locations are consistent with the hypothesis that nationwide seasonal changes such as photoperiod-dependent variation in host susceptibility may underlie pneumococcal seasonality, but caution is indicated in assigning causality as a result of such correlations.