Israel Medical Association Journal

Background: Guidelines for pandemic preparedness emphasize the role of sentinel and syndromic surveillance in monitoring pandemic spread.

Objectives: To examine advantages and obstacles of utilizing a sentinel influenza surveillance system to monitor community severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) activity based on Israel's experience from mid-March to mid-May 2020.

Methods: Several modifications were applied to the influenza surveillance system. The clinical component relied mainly on pneumonia and upper respiratory infection (URI) consultations with primary care physicians as well as visits to emergency departments (ED) due to pneumonia. The virological data were based on nasopharyngeal swabs obtained from symptomatic patients who visited outpatient clinics.

Results: By week 12 of the pandemic, the crude and age-specific primary physician consultation rates due to URI and pneumonia declined below the expected level, reaching nadir that lasted from week 15 until week 20. Similarly, ED visits due to pneumonia were significantly lower than expected from weeks 14 and 15 to week 20. The virological surveillance started on week 13 with 6/253 of the swabs (2.3%) positive for SARS-CoV-2. There was a peak of 13/225 positive swabs on week 145.8%. During weeks 17–20, none of the swabs (47–97 per week) were positive for SARS-CoV-2. This trend was similar to national data.

Conclusions: The virological component of the surveillance system showed the SARS-CoV-2 community spread, but had low sensitivity when virus activity was low. The clinical component, however, had no yield. Sentinel surveillance can assist in monitoring future novel pandemics and should be augmented in revised preparedness plans.

Background: Syndromic surveillance systems have been developed for early detection of bioterrorist attacks, but few validation studies exist for these systems and their efficacy has been questioned.

Objectives: To assess the capabilities of a syndromic surveillance system based on community clinics in conjunction with the WSARE[1] algorithm in identifying early signals of a localized unusual influenza outbreak.

Methods: This retrospective study used data on a documented influenza B outbreak in an elementary school in central Israel. The WSARE algorithm for anomalous pattern detection was applied to individual records of daily patient visits to clinics of one of the four health management organizations in the country.

Results: Two successive significant anomalies were detected in the HMO’s[2] data set that could signal the influenza outbreak. If data were available for analysis in real time, the first anomaly could be detected on day 3 of the outbreak, 1 day after the school principal reported the outbreak to the public health authorities.

Conclusions: Early detection is difficult in this type of fast-developing institutionalized outbreak. However, the information derived from WSARE could help define the outbreak in terms of time, place and the population at risk.

Contamination of food with streptococci could present with unusual outbreaks that may be difficult to recognize in the early stages. This is demonstrated in a large food-borne outbreak of streptococcal pharyngitis that occurred in 2003 in a factory in Israel. The outbreak was reported to the public health services on July 2 and an epidemiologic investigation was initiated. Cases and controls were interviewed and throat swabs taken. An estimated 212 cases occurred within the first 4 days, the peak occurring on the second day. There was a wave of secondary cases during an additional 11 days. The early signs were of a respiratory illness including sore throat, weakness and fever, with high absenteeism rates suggesting a respiratory illness. As part of a case-control study, cases and controls were interviewed and throat swabs taken. Illness was significantly associated with consumption of egg-mayonnaise salad (odds ratio 4.2, 95% confidence interval 1.4–12.6), suggesting an incubation period of 12–96 hours. The initial respiratory signs of food-borne streptococcal pharyngitis outbreaks could delay the identification of the vehicle of transmission. This could be particularly problematic in the event of deliberate contamination.

Objectives: To estimate usual patterns of acute illness in the community as a baseline for integration into pandemic influenza and bioterrorism preparedness plans.

Methods: Between 2000 and 2003 we conducted 13 telephone surveys to estimate the usual incidence and prevalence of symptoms of acute illness in the community.

Results: On average, 910 households were included in each of the surveys, representing about 3000 people. The compliance rates for full interviews ranged from 72.3% to 86.0%. In winter, on average, about 2% of the Israeli population (individuals) suffered each day from fever of ≥ 38ºC, and about 0.8% during the other months. The prevalence of cough was higher, 9.2% in winter and 3% during summer. Daily incidence of fever ranged from about 0.4% per day in winter to about 0.2% in the fall. The prevalence and incidence of both fever and cough were highest for infants followed by children aged 1–5 years.

Conclusions: These background morbidity estimates can be used for planning the overall treatment requirements, in addition to actual cases, resulting from pandemic influenza or a bioterrorist incident.

The appearance of “new” infectious diseases, the reemergence of “old” infectious diseases, and the deliberate introduction of infectious diseases through bioterrorism has highlighted the need for improved and innovative infectious disease surveillance systems. A review of publications reveals that traditional current surveillance systems are generally based on the recognition of a clear increase in diagnosed cases before an outbreak can be identified. For early detection of bioterrorist-initiated outbreaks, the sensitivity and timeliness of the systems need to be improved. Systems based on syndromic surveillance are being developed using technologies such as electronic reporting and the internet. The reporting sources include community physicians, public health laboratories, emergency rooms, intensive care units, district health offices, and hospital admission and discharge systems. The acid test of any system will be the ability to provide analyses and interpretations of the data that will serve the goals of the system. Such analytical methods are still in the early stages of development.