Plague is a highly virulent zoonotic disease caused by Yersinia pestis, a Gram-negative, facultatively anaerobic coccobacillus. This pathogen primarily circulates among rodent populations and is transmitted to humans through the bite of infected fleas. Additional transmission routes include direct contact with infected animal tissue or inhalation of respiratory droplets from individuals with pneumonic plague. These multiple transmission pathways highlight the bacterium’s potential for rapid...

Rocky Mountain Spotted Fever (RMSF) is a severe tick-borne illness caused by Rickettsia rickettsii, a Gram-negative, coccobacillary bacterium. This pathogen is an obligate intracellular parasite, requiring a host cell for replication. Transmission occurs through the bite of an infected tick. In the United States, the most important vectors are Dermacentor variabilis (American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick), though other tick species may also serve as vectors.

Chagas disease, or American trypanosomiasis, is a vector-borne parasitic infection caused by Trypanosoma cruzi, a flagellated protozoan (kinetoplastid) of the family Trypanosomatidae. The disease is endemic in Latin America, although cases are increasingly reported worldwide due to human migration. Transmission most commonly occurs when feces of infected triatomine bugs contaminate bite wounds or mucosal surfaces; additional routes include congenital, transfusional, transplant-related, and oral...

Pyelonephritis is a bacterial infection that primarily affects the renal parenchyma and collecting system, including the renal pelvis, tubules, and interstitial tissue of one or both kidneys. It can be classified as either acute—a sudden, severe infection—or chronic, which refers to long-term or recurrent kidney infections.The primary cause of acute pyelonephritis (APN) is bacterial infection, with Escherichia coli accounting for approximately 70-80% of cases. Other bacteria, such as Proteus,...

Yellow fever is a viral hemorrhagic disease caused by the yellow fever virus (YFV), a member of the Flaviviridae family. It is transmitted primarily by Aedes and Haemagogus mosquitoes in tropical and subtropical regions of Africa and South America. After transmission through a mosquito bite, the virus initially replicates in skin-resident immune cells such as dendritic cells and macrophages. These cells then migrate to the lymph nodes, where viral replication increases, eventually leading to...

Arboviral encephalitis refers to brain inflammation caused by arthropod-borne viruses, particularly those transmitted through mosquito vectors. Among these, West Nile virus (WNV), a member of the Flaviviridae family, is a significant public health concern. WNV is an enveloped, positive-sense, single-stranded RNA virus. Human infection typically begins when an infected mosquito introduces the virus into the dermis during feeding. The primary transmission cycle involves birds as amplifying hosts...