This is the first evaluation of the effects of integrating rapid testing for influenza into public health surveillance. Surveillance incorporating rapid tests greatly increased the number of specimens submitted for viral culture and the number of influenza isolates obtained. This finding is important because enhancing our capacity to recover circulating influenza virus isolates is the first step in establishing a robust virologic surveillance system designed to detect novel viral strains with pandemic potential.
Although physicians were permitted to send specimens directly to HDOH for viral culture, most of the influenza culture specimens submitted during the 1999-2000 and 2000-01 seasons were collected concurrently with a specimen for rapid testing. The fact that so few culture specimens were collected without a companion specimen for rapid testing implies that many physicians felt there was value to having both a culture and rapid test result, or alternatively, that the rapid test served as an incentive to obtain a culture.
The dramatic increase in the number of physicians who participated in the enhanced influenza surveillance project as compared to standard virologic surveillance suggests that the availability of the rapid test may have appealed to a larger cohort of clinicians. The involvement of a greater number of physicians is a promising development because public health officials may ultimately be able to obtain a more extensive and representative sample of circulating influenza isolates by broadening the pool of patients sampled.
This assessment is limited in that it lacks a control group consisting of physicians and laboratories that did not have access to the free rapid influenza tests for comparison once the enhanced virologic influenza project was initiated, beginning with the 1999-2000 influenza season. Instead, we compared the number of specimens received during the 1999-2000 and 2000-01 influenza seasons to the number received in the two prior seasons. Because the severity of annual influenza seasons can vary greatly from year to year, it could be argued that the increased number of specimens submitted during the latter seasons was secondary to increased numbers of influenza-like illnesses during those seasons. Several sources of information suggest this was not the case, however. First, influenza-like illness surveillance in Hawaii over the 4-year period does not suggest that influenza activity was markedly increased during the last two seasons. Second, the number of influenza cultures performed at laboratories on the mainland during the 1999-2000 season did not increase over the previous season to the extent observed in Hawaii. Third, CDC’s published assessment of the 1999-2000 influenza season was that the “season’s activity was similar to the previous two” and influenza activity during the 2000-01 season was assessed as “moderate and lower than the previous three seasons” (12
During the first season in which rapid tests were introduced, HDOH was unprepared for the increased numbers of submissions for influenza culture. HPHVL reported that the high volume of specimens received during the peak period placed an unexpected strain on virology section’s resources and that shortages in host cells, incubator space, and laboratory supplies resulted in a delay of several weeks for processing approximately 100 specimens (S. Naka, pers. comm.). The increased workload from processing specimens at HPHVL greatly reduced the laboratory’s resources for subtyping the influenza A isolates obtained that season. While recovering isolates is a critical first step in developing our capacity for influenza surveillance, to truly improve pandemic preparedness any increases in virus isolation must be coupled with expanded subtyping of influenza A isolates. Recognizing this, and with the experience gained from the prior year, adjustments in staffing and procurement permitted 79% of the influenza A isolates to be subtyped during the 2000-01 season.
Because of the difficulties encountered in processing specimens during the 1999-2000 influenza season, we limited our assessment of the influenza rapid test as compared to culture to specimens received in the 2000-01 season. This project was not designed as an evaluation of the rapid influenza test: We did not control for patient selection, specimen collection, or laboratory technique. Therefore, the findings from this field evaluation may not represent the rapid test’s performance in other settings. Other assessments on the performance of influenza rapid tests are available (5
Finding that isolates recovered during the influenza season increased when we integrated influenza rapid testing into our surveillance system should help allay concerns that adopting these tests will undermine virologic surveillance. If rapid influenza tests become an established component of clinical management, it will be difficult to convince clinicians to collect culture specimens in lieu of performing rapid tests (7
). Collection of a second specimen for culture confirmation, on the other hand, may be seen as clinically appropriate. Therefore, public health agencies may ultimately benefit from incorporating rapid diagnostic tests into influenza surveillance programs.
None of the commercial laboratories that participated in this project were independently offering rapid influenza testing before the 1999-2000 season. Through this initiative, each of the laboratories gained a level of proficiency in performing the rapid influenza test, and physicians became familiar with ordering the test. Once rapid influenza testing becomes established in laboratory and clinical practice, the question of whether providers will continue to opt for a rapid test and viral culture provided by a public health agency, or simply order a rapid test from a private laboratory at the patient’s expense, is still unanswered.
Although Hawaii’s Enhanced Influenza Virologic Surveillance program is a good model of a public-private partnership (16)
, we have one potential concern about the impact of using rapid influenza tests on public health surveillance. To date, at least two private influenza surveillance systems using rapid tests have been established--one by a manufacturer of a rapid test kit and the other by a pharmaceutical company that produces an anti-influenza medication (17
). Large private disease surveillance systems are relatively new to medicine. Because the chief concern of these proprietary systems is likely to increase sales of a product, it is not clear what role they will play in protecting the public health. If private surveillance systems compete with public agencies for physician participation, they may adversely affect virologic influenza surveillance.
In summary, our findings demonstrate that rapid influenza tests can be successfully integrated into public health surveillance efforts, resulting in a larger number of influenza isolates being available for subtyping and antigenic characterization. This enhanced influenza surveillance effort was accomplished through mutually beneficial public-private partnerships with commercial laboratories that routinely provide service to community physicians and their patients. Preparing for the next influenza pandemic compels public health agencies to work with physicians to expand our capacity for influenza surveillance. As the available data indicate that recent influenza pandemic strains have originated in Asia, vigilant virologic surveillance is especially important for Hawaii (19)
. Should an anomalous influenza strain emerge from Asia again in the future, our state’s unique geographic location and visitor profile make it likely that our population will be among the first in the United States to encounter this new pathogen.