Case Presentation: A 71 years old female with a history of hypertension presented with nausea, vomiting, and fall. She had non-bloody, non-bilious emesis after eating pork 2 days prior to admission. She worked in a kindergarten with no definitive sick contacts. She did not have abdominal pain or diarrhea but she experienced lightheadedness. She was found on the floor by her family and the patient stated that she lost her balance and fell. She denied head trauma or loss of consciousness. She had no focal weakness or numbness though complained of joint pains.On admission, the patient was hypotensive and tachycardic. She had hypokalemia, AKI, and leukocytosis. Her HS-troponin and BNP were elevated. Her EKG showed non-specific ST/T wave flattening and her transthoracic ECHO showed regional wall motion abnormalities. Her joint/extremity X-ray was unremarkable. Her chest X-ray revealed pulmonary vascular congestion and a left basilar density obscuring the hemidiaphragm, possibly atelectasis. Her respiratory panel was negative and there was no stool for a gastrointestinal panel. The patient was initially admitted for near syncope and fall with AKI thought to be caused by viral or bacterial gastritis, which improved clinically with supportive care. The patient, however, became more lethargic over the course of the admission and on day 3 developed nuchal rigidity, diaphoresis, and tachypnea. Rapid response was called, empiric antibiotics were initiated, and the patient was transferred to ICU with BiPap. Her repeat chest X-ray showed a right lower lobe infiltrate. LP was done in the ICU and CSF PCR panel was positive for Haemophilus Influenzae (H flu). Her blood culture also grew H flu serotype a (Hia). Antibiotics were narrowed to ceftriaxone. The patient finished 14 days of ceftriaxone with marked clinical improvement and was discharged to a subacute rehab facility.

Discussion: Hia can cause invasive diseases like Hi serotype b (Hib); however, the Hia vaccine is not available. Since the introduction of Hib vaccination in the late 1980s, overall invasive H flu disease dramatically decreased (1), however, invasive H flu infections due to non-Hib began to increase in 2000. Compared with 2002–2008, the estimated incidence of invasive H flu increased by 16% in 2009-2015, driven by increases in Hia and non-typeable infection (2). A surveillance study from 2008-2017 in the US showed an annual incidence of 0.1 for invasive Hia infection. The incidence in the age group over 65 years old was 0.14, the third highest after the age group 0-1 and 1-4 years old. Of note, the case-fatality ratio is highest among adults aged over 65 years (15.1%) (3). The incubation period for H flu infection is unknown. In adults aged over 50, the most common manifestation of H flu is pneumonia, followed by meningitis (4). Other common manifestations of invasive H flu include bacteremia, cellulitis, sore throat, and joint infections (5). The initial chest X-ray of our patient may have shown early signs of pneumonia in the right lower/middle lobe, which was obscured by lung markings in the hilar region or cardiac shadow.

Conclusions: For elderly patients who present with nausea and declining mental status, since the incubation period is unclear, meningoencephalitis should be considered. Additionally, for those who have respiratory symptoms, invasive H flu disease should be on the differential, especially for patients with close contact with children. For patients who met SIRS criteria with possible signs of infection in chest X-ray, an early CT chest might be beneficial (6).