Malaria Malaria, an acute infectious disease, is caused by protozoa of the genus Plasmodium— P. falciparum, P. vivax, P. malariae, P. ovale, and a more recent species, P. knowlesi—all of…

Lymphangitis The lymphatic system consists of a network of vessels, glands, and organs and functions as part of the immune system. The lymphatic system is also responsible for transporting fluids,…

Lyme Disease A multisystemic disorder, Lyme disease is caused by the spirochete Borrelia burgdorferi, which is carried by Ixodes scapularis, Ixodes pacificus, and other ticks in the Ixodidae family. The…

Listeriosis Listeriosis is an infection caused by the weakly hemolytic, gram-positive bacillus Listeria monocytogenes, which has been found in soil, wood, and decaying plant matter in the natural environment. The…

Leptospirosis Contact Precautions Leptospirosis is caused by Leptospira spirochetes and is considered the most common zoonosis in the world. The disease usually involves an acute phase with severe illness, followed…

Leprosy Contact Precautions Leprosy, also known as Hansen’s disease, is a chronic, systemic infection characterized by progressive cutaneous lesions. With timely and appropriate treatment, leprosy has a good prognosis; left…

Leishmaniasis Leishmaniasis is a protozoal disease that manifests in cutaneous, mucocutaneous, visceral, and viscerotropic forms. Cutaneous disease may be classified as localized, diffuse, leishmaniasis recidivans or post-kala-azar dermal leishmaniasis. The…

Legionellosis Infections caused by species of the genus Legionella are collectively termed legionellosis, or Legionnaires’ disease. Legionellosis is an acute bronchopneumonia produced by the gram-negative bacillus L. pneumophila. Outbreaks usually…

Influenza, Seasonal Droplet Precautions Influenza (also called the grippe or the flu) is an acute, highly contagious infection of the respiratory tract caused by influenza viruses from the family Orthomyxoviridae….

Influenza, H5N1 Contact Precautions Droplet Precautions Airborne Precautions Influenza H5N1, also known as avian influenza (flu), mainly infects birds but is also of concern to humans, who have no immunity…