key: cord-0009291-bcm57i3v
authors: Chen, Kuan-Fu; Gaydos, Charlotte; Rothman, Richard E.
title: Commentary
date: 2009-10-23
journal: Ann Emerg Med
DOI: 10.1016/j.annemergmed.2009.09.010
sha: 8867824c3dd23c811d0ca0cb4031afe1912785e3
doc_id: 9291
cord_uid: bcm57i3v

nan

leg swelling. She was wheelchair bound and had no recent history of travel or known contact with ill persons. In the ED, the patient was afebrile, with a blood pressure of 57/39 mm Hg, pulse 57 beats/min, respiratory rate of 14 breaths/min, and oxygen saturation of 87% on room air. ECG was suggestive of non-Q-wave myocardial infarction. Chest radiograph showed bilateral pneumonia and congestive heart failure with marked cardiomegaly. Her laboratory abnormalities included an increased WBC count of 13.4 cells/mm 3 , mild anemia with a hematocrit level of 34%, a mildly increased creatinine level at 1.8 mg/dL, alanine aminotransferase level of 36 units/L and aspartate aminotransferase level of 160 units/L, and markedly increased troponin and creatinine kinase levels of 29.43 ng/mL and 653 IU/L, respectively. The patient went into respiratory arrest, was subsequently tracheally intubated, began receiving low-dose dopamine, and was admitted to the ICU with a diagnosis of myocardial infarction, congestive heart failure, pneumonia, and presumed sepsis. A chest computed tomography scan showed complete atelectasis of the right middle lobe, bilateral ground-glass opacities of the upper lobes, and bilateral pleural effusions. A subsequent bronchoscopy identified a large cauliflower-shaped mass in the right lower lobe airway. Multiple blood, urine, and sputum cultures were unrevealing; rapid antigen test was positive for influenza A, with subsequent confirmation novel influenza A (H1N1) at the CDPH VRDL. The patient remains hospitalized in critical condition under intensive care.

Initial surveillance for hospitalized patients with of novel influenza A (H1N1) infection in California indicates that the majority of patients were discharged after short hospital stays. Previously healthy patients without underlying chronic medical conditions recovered, with an uncomplicated hospital course and a median length of stay of 2.5 days (range 1 to 7 days). Although one-third of hospitalized patients had abnormal chest radiograph results with multilobar infiltrates, only 9% were treated with oseltamivir; nonetheless, most had favorable outcomes. Of 5 pregnant women, 2 developed serious sequelae; however, the role that preceding infection with novel influenza A (H1N1) played in these outcomes is unclear.

Certain hospitalized patients in California experienced severe disease and prolonged hospital courses. Of note, 3 of the 6 California patients admitted to an ICU continue to require prolonged intensive care. Extremes in age and multiple and debilitating underlying medical conditions might be contributing to the severity of illness in these patients. Although chronic underlying medical conditions and pregnancy classically are associated with a greater risk for complications for seasonal influenza, 6 one patient (patient 18) who was relatively healthy, with only mild chronic pulmonary disease, required intensive care and mechanical ventilation. More data are needed about which populations are at greatest risk for hospitalization and severe sequelae after infection with novel influenza A (H1N1).

As of May 15, 2009, 9% of approximately 11,600 clinical specimens submitted for testing to California public health laboratories since April 27, 2009, were positive by rRT-PCR for influenza A; of those, 23% and 28% were subtyped as seasonal influenza A/H1 and A/H3, respectively. These results indicate that seasonal influenza viruses continue to circulate throughout California and might be a cause of influenza-like illness and positive results from rapid antigen tests. Although rapid antigen test results were positive in 67% of tested cases in this series, anecdotal reports from other cases confirmed at the CDPH VRDL, tested mostly in the outpatient setting, suggest that false-positive and -negative results are common. Accordingly, the CDPH has emphasized the importance of testing influenza viruses in the state with rRT-PCR. The CDPH also has advised clinicians in California to collect respiratory specimens for rRT-PCR testing, subtyping, and further characterization at public health laboratories from patients who are hospitalized or who die with febrile respiratory illness.

Additional information about novel influenza A (H1N1) treatment guidance and other CDC recommendations is available at http://www.cdc.gov/h1n1flu/guidance. On June 11, 2009, less than 1 month after the release of this first report of hospitalized patients with novel influenza A (H1N1), the World Health Organization declared an influenza pandemic, urging the health care community to implement appropriate measures to help prevent a repeat of the deadly 1918 pandemic, which caused more than 50 million deaths. Although most cases observed during the current outbreak appear to be relatively mild (as of July 11, 2009 , there were approximately 37,000 US cases, with slightly more than 200 deaths), serious complications have occurred and the pandemic remains in flux. Emergency physicians will play a pivotal role in the care of patients during this infectious disease outbreak and accordingly need to be armed with guidance to reduce morbidity and mortality and decrease likelihood of disease transmission. Key ED management issues include triage and isolation, diagnostic testing, and disposition. This discussion addresses these issues, which have also been the focus of recent guidance from American College of Emergency Physicians (ACEP) leadership. 1,2

EDs act as major sites for transmission of respiratory viruses, as evidenced with severe acute respiratory syndrome. 3 Seasonal influenza spreads principally by droplet transmission, ie, coughing or sneezing occurring over short (Ͻ6 feet) distances 4 and less commonly by contact transmission (ie, skin to skin or fomite). Airborne transmission, ie, dissemination of small droplet nuclei or particles occurring over longer distances, is also believed to occur, but this mode remains controversial and is likely far less frequent. 5 Limited data are available about transmission modes for novel influenza A (H1N1), but the CDC and others report that patterns are likely similar to those of seasonal influenza but with higher transmissibility. 6, 7 Resources recently created and regularly updated by the CDC and ACEP have been made available to guide clinical decisionmaking. 2, 8 Droplet precautions are advised for any patient presenting with "symptoms of an acute respiratory infection." 2 For waiting room patients, this means physical separation of symptomatic and asymptomatic patients, with distribution of surgical masks for those with active respiratory symptoms. 2 Alternative temporary open-air waiting areas (eg, tents) are advised according to ED capacity. The triage process should include specific criteria to identify suspected cases among individuals with influenza-like illness, ie, temperature greater or equal to 37.8°C (100°F) plus cough or sore throat in the absence of a known cause other than influenza. Suspected cases are then identified as any patient with influenza-like illness who has had contact with anyone with a confirmed case, travel to a region with greater than 1 confirmed case, or residence in a community with greater than 1 confirmed case. Although early in the outbreak the CDC recommended airborne precautions with N95 mask use for health care workers caring for those with suspected or confirmed cases, guidelines have since evolved. The most recent ACEP and Society for Healthcare Epidemiology of America (SHEA) recommendations advise droplet precautions only, with the following exceptions: for patients requiring supplemental oxygen, add private room with closed door, and in instances in which respiratory procedures are being performed (ie, intubation, nebulizer treatment, suction, sputum induction), patients should be placed in an airborne isolation room. 2 Notably, a recent Morbidity and Mortality Weekly Report found that a significant proportion of health care worker-acquired cases of novel influenza A (H1N1) infections occurred among those with inconsistent use of personal protective equipment. 9 The most common breaches were failure to adhere to eye protection, followed by failure to adhere to use of surgical or N95 masks.

Diagnostic tests available for influenza detection include those that are rapid (enzyme immunoassays or immunochromatographic assays). Rapid testing can be done at the bedside, with turnaround times of 10 to 30 minutes, but most EDs still rely on the central laboratory, resulting in turnaround times of 1 to 4 hours. An important limitation of rapid tests is their inability to distinguish between seasonal and novel influenza A (H1N1) viruses. There are also a variety of other slower but more sensitive and specific tests that require central laboratories for processing. These include direct immunofluorescence, polymerase chain reaction, serology, and viral culture.

In this Morbidity and Mortality Weekly Report, 10 a significant number of false-negative rapid tests were reported. Notably, high rates of false-positive results have also recently been observed, a phenomenon known to occur early in any epidemic, when prevalence of disease is relatively low. 11 Thus, although rapid antigen tests have the merit of timeliness, emergency physicians need to be aware of their limitations. For seasonal influenza, the sensitivity of commercially available rapid influenza tests ranges from 50% to 70%. 11 As of yet, limited data are available about rapid test performance for novel influenza A (H1N1), although at least 1 recent study reports a sensitivity of only 10% to 30%. 12 At Johns Hopkins Hospital (A. Valsamakis, oral communication), we have abandoned use of rapid testing according to similarly poor sensitivity.

Which ED patients should be tested is a complex and evolving issue. Currently, the CDC generically recommends testing persons if they have "an acute febrile respiratory illness or sepsis-like syndrome." Guidelines also note that the very young, old, and immunocompromised may have atypical presentations. More practically for the ED, the CDC advises that those with "mild illnesses or those residing in affected areas need not be tested," with priority given to those for whom hospitalization is being considered or those at high risk for complications. 4 Testing of patients who will be admitted is important for isolation decisions (generally inpatient cohorting); testing in high-risk populations is important for treatment decisions.

Disposition decisionmaking is critical for patient safety, hospital resource utilization, and control of nosocomial infections. At this point, there are insufficient data to reliably determine precisely who is at greatest risk for complications. 13, 14 Both the CDC and ACEP thus suggest that risk-stratification decisions for novel influenza A (H1N1) be based on the same age and risk categories used for seasonal influenza. Younger children, older adults, immunocompromised individuals, nursing home patients, pregnant women, and those with chronic underlying diseases are considered at increased risk. 2 Although this early report suggests that most patients infected with novel influenza A (H1N1) in the United States have recovered quickly, with relatively short lengths of stay (median 2.5 days for those without underlying conditions), some prolonged hospitalizations and complications were observed. Not surprisingly, the majority occurred in those with chronic underlying conditions (see the table in the full CDC text for details). 10 Several recent reports implicate that pregnancy and obesity are associated with increased risk of complications. 15, 16 A surprising dearth of clinical prediction rules exist to aid disposition decisionmaking for those with seasonal influenza, with the exception of one that has been validated for adult patients older than 65 years. 17 In that study, risk factors for hospitalization or death included increasing age, male sex, previous-year hospitalization for pneumonia or influenza, increased number of outpatient visits, and presence of pulmonary disease, cardiac disease, renal disease, dementia, stroke, or cancer. In a recent pilot study, we used influenza viral load as a surrogate to predict hospital length of stay. 18 Future work is required to develop and validate clinical or biomarker prediction guidance for the novel influenza A (H1N1) infection. For now, emergency physicians should remain alert to ongoing clinical and epidemiologic data, local regulations, and the most up-to-date guidance from both the CDC and ACEP. 

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