Rats can develop the infection, and help spread the infection to other fleas that bite them, and help multiply the number of infected fleas that can then infect humans. Less often, endemic typhus is caused by Rickettsia felis and transmitted by fleas carried by cats or opossums. In the United States of America, murine typhus is found most commonly in southern California, Texas and Hawaii. In some studies, up to 13% of children were found to have serological evidence of infection. Diagnosis
As of 2014, early diagnosis continued to be based on clinical suspicion, and treatment of the disease is indicated even before laboratory results confirm its presence. Because of the lag between the onset of infection and the appearance of antibodies in a blood test, serologic tests are merely confirmatory and retrospective. Weil-Felix agglutination reactions are not sensitive to the disease. Indirect fluorescence antibody assays  that are specific to R. typhi antigens are the recommended route for detection and diagnosis: diagnostic titers are present in half of all cases within the first week of infection and in nearly all cases by day-15. The sharing of antigens by rickettsiae means routine serologic evaluation will not distinguish between murine typhus and epidemic typhus. Bacterial cultures are rarely performed because although they are highly accurate for diagnosis, the biohazard risk of generating them is often considered too high. Treatment
The disease can be fatal if left untreated, but endemic typhus is highly treatable with antibiotics.
Use of dexamethasone (Decadron) 4–8 mg IV q 8 - 12 h in cases where airway edema may be the cause of the stridor; note that some time (in the range of hours) may be needed for dexamethasone to work fully. Use of inhaled Heliox (70% helium, 30% oxygen); the effect is almost instantaneous. Helium, being a less dense gas than nitrogen, reduces turbulent flow through the airways. Always ensure an open airway.In obese patients elevation of the panniculus has shown to relieve symptoms by 80%. References
External links

Audio Breath Sounds Archived 2020-12-15 at the Wayback Machine—Multiple case studies with audio files of lung sounds. Stridor at eMedicine
Congenital stridor at eMedicine
MedlinePlus Encyclopedia: Breathing sounds—abnormal (stridor)
Diseases Database (DDB): 27190
Stridor sounds at R.A.L.E. Lung Sounds