Article, Infectious Diseases

The transmission of the influenza virus from patient to emergency physician: No flu for you

a b s t r a c t

Background: Significant morbidity and mortality is attributed to infection with the influenza virus annually and care is often sought in Emergency Departments (ED). The exposure of Emergency Department healthcare per- sonnel and subsequent illness is speculated to be high but has not been quantified.

Methods: All physicians and mid-level providers in a large tertiary care ED who cared for an Influenza-positive patient were identified and surveyed. Information was gathered regarding each provider’s report of an influenza-like illness during the study period as well as laboratory testing results, sick contacts and subsequent missed work. General descriptive information of Influenza-positive patients was extracted through a retrospec- tive chart review.

Results: 1020 Influenza-positive patients were cared for by 106 physicians and advanced practice nurses. Patients testing positive for Influenza-A were more likely to be admitted (p = .003). The majority of patients (83%) were cared for by an attending only. Our provider survey response rate was 87%. 1 in 4 providers reported suffering from an Influenza-like illness during the study period and no providers subsequently missed work days. Only 4 (5%) of those providers sought medical care to receive testing. Overall, 2% of ED providers tested positive for Influenza.

Conclusions: Among Emergency Department providers, transmission of clinically significant Influenza illness was low.

(C) 2019

Introduction

Infection with the influenza virus can cause significant morbidity and mortality. This is especially true in vulnerable populations such as very young children, pregnant and recently postpartum, the immuno- compromised and the elderly. Multiple deaths are attributed to the in- fluenza virus whether primarily or secondarily. One study estimated the prevalence of symptomatic influenza in the United States to be ap- proximately 8% [1]. Influenza is spread from person to person contact via droplets produced when infected people sneeze, talk or cough. These droplets can travel up to six feet and can remain infectious on hard surfaces for up to 24 h. The median incubation period for influenza A ranges from 1 to 9 days and for Influenza B the median period is 0-6 days [2]. The “influenza season” occurs during the fall and winter months reflecting the increased activity and transmissibility of the virus. Each year thousands of patients seek evaluation in Emergency De- partments (EDs) for Influenza and influenza-like illnesses and are often admitted for the same. Emergency Department healthcare providers are

* Corresponding author.

E-mail address: [email protected] (J. Kashani).

in frequent contact with suspected influenza patients who are actively symptomatic while seeking care. As such, they are at risk of acquiring in- fluenza in the workplace and subsequently infecting other Healthcare workers, patients, or Emergency Department visitors. According to the Centers for Disease Control (CDC), The burden of Influenza during the 2017-2018 season was the highest since the 2009 pandemic, resulting in N22.7 million medical visits, 959,000 hospitalizations, and 79,400 deaths (cdc.gov).

Healthcare providers are encouraged, and oftentimes mandated to receive the Influenza vaccine. This is thought to serve a two-fold pur- pose; to decrease the susceptibility of acquiring the influenza virus and to contribute to herd immunity to protect susceptible populations. There may also be secondary benefits such as decreased loss of produc- tivity through a decrease in missed work days [3]. Although conceptu- ally vaccination could confer absolute protection from acquiring the influenza virus, the effectiveness can vary. Any discordance between the vaccine strain(s) and the prevalent strain will decrease vaccine ef- fectiveness. For the 2017-2018 influenza season, the CDC reported an estimated 40% vaccine effectiveness (cdc.gov). Since these statistics are derived from the outpatient setting, the results may not be general- izable to healthcare workers. The true protection given to those who are vaccinated is largely unknown.

https://doi.org/10.1016/j.ajem.2019.05.051 0735-6757/(C) 2019

K. D’Amore et al. / American Journal of Emergency Medicine 38 (2020) 562565 563

We did not find any previously published studies that measure the transmissibility of the influenza virus from patient to healthcare pro- vider. Given the close contact of Emergency Medicine Physicians to their patients, we believe that a significant risk of transmission to healthcare providers exists. The aim of our study was to attempt to quantify the transmission of influenza from infected patient to Emer- gency Department provider. We hypothesize that the transmission would be high and more frequent among those providers with more pa- tient exposures. This IRB approved study was conducted at St. Joseph’s University Medical Center in Paterson New Jersey. St. Joseph’s is the

Table 1

Characteristics of influenza emergency department visits.

Characteristic Influenza A positive (N = 709)

Gender (%) Male

45.1 (320)

46.6 (145)

Female

54.9 (389)

53.4 (166)

Age (mean, years)

Adult (N18)

61.5 (436)

62 (193)

Pediatric (b18)

38.5 (273)

38 (118)

Disposition (%)

Influenza B positive (N = 311)

busiest single site Emergency Department in New Jersey, seeing up- wards of 170,000 visits annually, with over 40,000 pediatric visits.

Materials and methods

We conducted a retrospective chart review during the Influenza sea- son which was defined as the calendar months of September through May. A search of the electronic medical record (MEDHOST) was per- formed for all discharge or admission diagnoses containing the word “influenza” for all patients seen and evaluated in the Adult or Pediatric

Admission Discharge

Month (%) September October November December January February March April

May

16.6 (118)

83.3 (591)

0.3 (2)

0.4 (3)

1.0 (7)

2.5 (18)

21.6 (153)

30.7 (218)

3.4 (24)

1.1 (8)

0.4 (3)

9.6 (30)

90.4 (281)

0 (0)

0 (0)

1.0 (3)

1.0 (3)

12.5 (39)

35.0 (109)

8.0 (25)

4.5 (14)

0 (0)

Emergency Department from September 1, 2017 through May 31, 2018. A chart review was then performed to determine which patients had a positive Influenza test performed in the Emergency Department on the date of presentation. Patients for which an Influenza nasal swab test was not performed and those who tested negative for influ- enza were excluded. Our study population was any aged patient who was diagnosed with Influenza after a positive Influenza nasal swab test (whether Strain A or B) in our Emergency Department.

Once patients were identified, we gathered information regarding the attending physician and resident physician (if applicable), the strain of influenza, as well as the ultimate disposition of the patient. A com- plete list of all attending physicians and mid-level providers (resident physicians, Advanced Practice Nurses) who cared for at least one Influ- enza positive patient was compiled. These physicians were asked to complete a survey (Appendix A) to ascertain whether they had suffered from Influenza or an Influenza-like illness during the study period in a time period suggestive of transmission in the workplace setting. Follow-up questions ascertained which physicians tested positive for Influenza, if there were subsequent missed-work days, and if there were any known sick contacts leading up to their illness. Surveys were conducted in person at each physicians’ convenience.

Data was compiled using Microsoft Excel. Data was cleaned and then analyzed using SAS University Edition 9.4.

Results

A total of 1343 patients were diagnosed with either Influenza A or Influenza B during their Emergency Department evaluation. Three hun- dred and twenty-three patients did not have a documented positive In- fluenza test and were excluded from further analysis. 1020 patients were included in the subsequent analyses. The mean age was 41 years (0-100 years) with 629 (60.2%) of these patients adults 18 years of age or older (Table 1). Fifty-four (54) percent of all patients were fe- male. The majority (85%) of influenza-positive patients were discharged from the Emergency Department.

January (28.8%) and February (51.7%) had the most ED Influenza di- agnoses. The predominant strain was Influenza A, accounting for 70% of all diagnoses. Those diagnosed with Influenza A were more likely to be admitted (p = .0035).

Fifty-three attending physicians, fifty resident physicians and three

Attending-only care (%) 82.9 (588) 83.6 (260)

Among providers, 25.3% (21) reported suffering from influenza or an influenza-like illness during the study period. Of those 21 providers, 4 were tested for Influenza and 2 tested positive (9.5%). One of the two providers recalled a sick contact outside of the Emergency Department with whom she was in contact around the time of her Influenza illness. This resulted in an overall Influenza-confirmed illness rate of 2.0%. There were no reported missed work days due to influenza. Those who reported an Influenza-like illness had less Influenza patient expo- sures as compared to those who did not report such an illness (Table 2).

Discussion

Influenza is a Public health concern and a significant cause of mor- bidity and mortality, especially in vulnerable populations such as the ge- riatric, pediatric, and immunocompromised. The Emergency Department is a crucial point of access for many suffering from Influ- enza and it is also a source of potential exposures for patients and healthcare providers alike. During Influenza season, the influx of pa- tients can result in long waiting room times, Emergency Department and Hospital overcrowding and can contribute to the boarding of pa- tients in Emergency Departments [4]. Two recent studies attempted to quantify the Influenza exposure of Emergency Department healthcare personnel. Rule et al. found that Influenza A viral copy numbers taken from ED personnel were more than twice that taken from swabs of the ED rooms themselves. They also found that even filtering respirators worn by those in close contact with Influenza patients could become contaminated with the virus and thus exposures were still possible [5]. Esteve-Esteve et al. reported that patients presenting to the Emer- gency Department were twice as likely to be diagnosed with Influenza than those presenting to outpatient clinics and this risk increased in pe- diatric patients younger than 15 years of age [6].

Although the effectiveness of influenza vaccine for the 2017-2018 influenza season was thought to be 40%, with “effectiveness” measured

Table 2

Influenza exposures.

Provider characteristic Mean number of influenza exposures (range)

Advanced Practice Nurses cared for these 1020 patients. The mean num- ber of exposures was 13.5. Among all mid-level providers the mean number of exposures was 4.6 and among attending physicians, the mean was 18.9 (Table 2). Of the 106 providers, surveys were adminis- tered to the 95 for which we had valid contact information. The overall survey response rate was 87.4% (83).

All providers Attending physician Mid-level provider

Reported influenza-like illness Yes

No

13.5 (1-80)

18.9 (1-80)

4.6 (1-18)

10.3

15.2

564 K. D’Amore et al. / American Journal of Emergency Medicine 38 (2020) 562565

by the decrease in a person’s overall risk to seek medical care for a flu- illness in a doctors office. In the 1990’s, Wilde et al. found a vaccine effi- cacy of 88% for influenza A and 89% for influenza B. This study was con- ducted over three consecutive years, from 1992 to 1995, and included 359 person-winters of serologic surveillance. Participants were ran- domly assigned to receive either an influenza vaccine or a control and had serological testing at the time of vaccination, 1 month after and the end of the influenza season. The authors concluded that the influ- enza vaccine is effective in preventing infection by influenza A and B in health care professionals [3]. An earlier study, conducted during the 1988-1989 A/H1N1 epidemic, demonstrated what the authors consid- ered an excellent protection conferred by the influenza vaccination in geriatric nursing home residents. Of 285 vaccinated patients, only one developed influenza. In the same study 20% of unvaccinated nursing home staff developed influenza [7]. A systematic review, conducted by Burls et al., analyzed 18 studies looking at the evidence for vaccination and its economic evaluation. Their results suggested that vaccination protects health care workers, provides indirect protection to the high risk while being cost effective and probably cost saving [8]. Interest- ingly, Elder et al. found that in 120 health care workers with seroposi- tive influenza tests 59% did not recall an influenza like illness and 28% did not recall any respiratory infection during their study period [9]. This raises the suspicion that a person may test seropositive for influ- enza and have a subclinical illness. Furthermore, the transmissibility of influenza during that period is difficult to define as the person with a subclinical illness may not be considered a sick contact.

In this study of transmissibility of the influenza virus from patient to healthcare provider in the Emergency Department, 1020 influenza- positive patients were cared for by 106 attending and resident physi- cians. Only 21 reported suffering from influenza or an influenza-like ill- ness during the study period with only 2 testing positive for Influenza. All off our study participants received the influenza vaccine and given the results of the previously mentioned studies, may have had a high level of protection from acquiring influenza in the workplace setting. Those providers who did suffer from Influenza or what they believed to be an Influenza-like illness, did not subsequently miss any work days. Additionally, those providers that became ill with Influenza had, on average, less documented Influenza patients than those providers who did not become ill. Thus in our population, provider care for quan- titatively more Influenza infected patients did not translate into in- creased incidence of PErsonal Influenza illness. In conclusion, despite a large volume of patients and potential exposures, our results show that there is low transmission of Influenza from patient to Emergency Department healthcare provider. The use of droplet precautions, hand washing and the wearing of patient masks may account for the low transmissibility found in our study. Furthermore, the utility of the influ- enza vaccine in preventing the acquisition of the influenza vaccine may be more effective than the 40% cited by the CDC.

Limitations

This study has several limitations. The reported sensitivity of the rapid Influenza nasal swab ranges from 50 to 70%, meaning that nearly half of patients testing negative may in fact be positive for the Influenza A or B virus. Furthermore, the CDC does not recommend Routine testing in patients who demonstrate signs and symptoms of an Influenza-like illness and who are not expected to be hospitalized, supporting a clinical diagnosis in those patients (cdc.gov). Our study excluded patients who were either not tested or had a negative swab and therefore, may have underestimated the true prevalence of Influenza in our Emergency De- partment. Given the nature of a retrospective study, there is the poten- tial that physicians may not recall having influenza or an influenza-like illness, and considering the results of Elder et al., there may have been a higher degree of influenza positive participants with subclinical illness. Furthermore, the reporting of an influenza-like illness or the diagnosis of influenza may not be related to their workplace exposure. We also

did not ascertain which healthcare provider performed the influenza swab on infected patients as this likely varied from patient encounters and may have been performed by the nurse or other staff members. Pre- sumably, those performing the swab would have closer contact and thus be at increased risk for acquiring the influenza virus. In addition, in the cases of the patient having both a resident and attending physi- cian on record, we could not comment on the extent of contact by either of the healthcare providers. We only surveyed providers who treated influenza-positive patients in our Emergency Department. Therefore, there may have been providers who were not surveyed but did suffer from influenza and potentially contracted it from patients treated else- where (e.g. other EDs where the provider is employed). Finally, it is im- possible to account for all the exposures to the influenza virus, both in the workplace and outside of the workplace. Our study, however, as- sumed that a relationship exists between patient contact and acquiring influenza and it can logically be assumed that healthcare providers are exposed to more people with influenza than those not working in the healthcare setting. The incubation period and transmissibility of the in- fluenza viruses makes a direct relationship between the two speculative at best.

Conclusion

Infection with the influenza virus can result in significant morbidity, mortality and missed work days. We believe that our study demon- strated a low rate of transmission from patient to health care provider in the Emergency Department. This low rate may be attributed to pri- mary precautions such as vaccination, hand washing, and placing masks on patients with suspected Influenza. Given the lack of absolute protection of acquiring influenza in those vaccinated and the increased exposure of influenza positive in patients in the Emergency Department setting, we believe that our study has scientific bearing.

Meetings

None.

Grant

None.

Author contributions

KD and JK conceived the study, designed the study and data collec- tion, and obtained IRB approval. KD and JK supervised the conduct of the trial and data collection. KD, AS, and JK undertook data collection. KD and JK provided statistical advice on study design and analyzed the data; KD and JK drafted the manuscript, and all authors contributed sub- stantially to its revision. All authors take responsibility for the paper as a whole.

Declaration of Competing Interest

None.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2019.05.051.

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