Infectious diseases include an extensive group of diseases caused by specific pathogenic (pathogenic) pathogens and transmitted from an infected individual to a healthy one. The peculiarities of infectious diseases are their contagiousness (contagiousness), the ability to mass epidemic spread, the cyclical course and the formation of post-infectious immunity. However, these features are expressed to varying degrees in different diseases.

This type of disease develop as a result of a complex biological process of interaction of a pathogenic microorganism with a susceptible macroorganism under certain conditions. There are several periods in the development of infectious diseases: incubation (latent), prodromal (the period of precursors), the period of development of clinical manifestations, the period of the outcome of the disease. The outcome of the infectious process can develop in several ways: convalescence (recovery), lethality, bacterial carrier, transition to a chronic form.

Infectious diseases account for 20 to 40% of the total structure of human diseases. Many medical and microbiological disciplines are engaged in the study, treatment and prevention of infections: actually infectious diseases, epidemiology, venereology, urology, gynecology, therapy, phthisiology, otolaryngology, immunology, virology, etc.

The number of infectious diseases known to science is constantly increasing and currently has more than 1,200 units. During his life, a person comes into contact with a huge number of microorganisms, but only 1/30000 of this community is capable of causing infectious processes. Viruses, rickettsias, bacteria, fungi have pathogenicity properties.

Depending on the location of the predominant localization of the process and a certain mechanism of transmission, infectious diseases are divided into intestinal (dysentery, cholera, salmonellosis, escherichiosis, paratyphs A and B, typhoid fever, food toxicoinfections); respiratory tract infections (ARVI, influenza, chickenpox, measles, mycoplasma respiratory infection); external integuments (erysipelas, anthrax, scabies); blood infections (HIV infection, malaria, yellow fever, recurrent and typhus); infections with multiple transmission routes (enterovirus infections, infectious mononucleosis).

By the nature of the pathogen, infectious diseases are distinguished: viral (viral hepatitis A, B, D, E and C, influenza, rubella, measles, cytomegalovirus and herpes infections, HIV infection, meningococcal infection, hemorrhagic fevers); bacterial (staphylococcal and streptococcal infection, cholera, salmonellosis, plague, dysentery); protozoal (malaria, trichomoniasis, amoebiasis); mycoses or fungal infections (aspergillosis, candidiasis, epidermophytia, cryptococcosis).

Infectious diseases are divided into anthroponotic and zoonotic. Anthroponoses include infections peculiar exclusively to humans and transmitted from person to person (smallpox, diphtheria, typhoid fever, measles, dysentery, cholera, etc.). Zoonoses are animal diseases that can also infect humans (foot-and-mouth disease, anthrax, rabies, tularemia, plague, listeriosis, leptospirosis, brucellosis).

Diseases caused by pathogens of animal origin – parasites (ticks, insects, protozoa) are called invasive or parasitic.

Among infectious diseases, there is a group of particularly dangerous (quarantine) infections with a high degree of contagion, a tendency to rapid spread, a severe epidemic course and a high risk of death in the shortest possible time from the moment of infection. Plague, smallpox (considered eradicated in the world since 1980), cholera, yellow fever (and similar epidemiology of Marburg fever and Ebola) are classified as particularly dangerous infections by the World Health Organization. Tularemia and anthrax are also classified as particularly dangerous infections in our country.

Treatment of patients with infectious diseases is carried out in specialized hospitals or departments, in mild cases – at home. A prerequisite for the successful treatment of infections is compliance with a strict anti-epidemic regime. The prevention of most infectious diseases is the observance of sanitary and hygienic rules and specific immunization.

The medical directory of diseases posted on the website “Medic Journal” contains a special section – where you can find useful information about the causes, mechanisms of development and clinical manifestations of infections, as well as about modern diagnostic and therapeutic techniques used in this field of medicine.



Lymphadenitis is a nonspecific or specific inflammatory lesion of lymph nodes. Disease is characterized by local soreness and an increase in lymph nodes, headache, malaise, weakness, and an increase in body temperature. Diagnosis is carried out by collecting anamnesis and physical examination; the etiology is clarified by biopsy of the altered lymph node. Treatment is…

suppurative lymphadenitis

Suppurative Lymphadenitis

Suppurative lymphadenitis is a form of acute inflammation of the lymph nodes of a nonspecific or specific etiology, accompanied by the formation of purulent exudate. It is characterized by an increase, compaction, soreness of the affected area, redness of the skin, the appearance of a symptom of fluctuation, fever and other signs of intoxication of…

actinic keratosis

Actinic Keratosis

Actinic keratosis is a widespread (especially among the elderly) disease with a slow, steadily progressive course, the occurrence of which is provoked by exposure to direct sunlight on the skin. The primary element is an oval peeling spot localized in open areas of the skin, which quickly transforms into a keratoacanthoma – a benign neoplasm…

foot and mouth disease

Foot and Mouth Disease

Foot and mouth disease is an acute infectious disease of viral etiology characterized by vesicular erosive lesion of the integumentary tissues (mainly the mucous membranes of the mouth and the skin of the extremities), accompanied by intoxication syndrome. Foot and mouth disease infection occurs from livestock and wild animals mainly by contact, but a food…

japanese encephalitis

Japanese Encephalitis

Japanese encephalitis is a transmissible viral neuroinfection with a predominant lesion of the brain substance. It is characterized by endemic outbreaks in the period from August to the end of September. It has a general infectious origin, during the peak period, disorders of consciousness, meningeal syndrome, hyperkinesis, myoclonia, paresis, bulbar disorders are characteristic. Diagnostics involves…

e. coli infection

E. Coli Infection

E. coli infection is an acute, mainly intestinal infection caused by some serovars of the bacterium Escherichia coli. Escherichiosis manifests itself in the form of enteritis and enterocolitis, can be generalized and occur with extra-intestinal symptoms. The route of transmission of E. coli is fecal-oral. More often, infection occurs when eating infected dairy and meat…

pancreatic echinococcosis

Pancreatic Echinococcosis

Pancreatic echinococcosis is one of the forms of helminthiasis, which is caused by the larvae of the echinococcal tapeworm and leads to the formation of parasitic cysts in the pancreas. The disease is manifested by discomfort and pain in the epigastric region, nausea, and stool disorders. When the pancreatic ducts and gallbladder are compressed, skin…

hepatic echinococcosis

Hepatic Echinococcosis

Hepatic echinococcosis is one of the most common parasitic diseases, which is based on the formation of cysts in the liver. The main signs of this pathology are general weakness, a significant decrease in appetite, a decrease in body weight, a feeling of heaviness in the liver, nausea after eating fried or fatty foods, stool…



Echinococcosis is a parasitic invasion by the larval stage of the echinococcus tapeworm, occurring with damage to internal organs (liver, lungs, heart, brain, etc.) and the formation of echinococcal cysts in them. Nonspecific symptoms of echinococcosis include weakness, urticaria, transient fever; specific ones depend on the location of the parasite and can be represented by…



Ergotism is poisoning by ergot alkaloids trapped in flour, or taken as a medicine. Typical symptoms are convulsive muscle contractions, intense diarrhea, severe muscle pain, paresthesia, hallucinations, delirium. In severe cases, tissue necrosis occurs. With chronic pathology, amenorrhea is observed in women. Diagnosis of the disease is based on clinical data, careful collection of anamnesis,…