Influenza: Diagnosis, Treatment, Prevention - V.D. Moskaliuk 2010

Influenza

Influenza is an acute anthroponotic viral disease transmitted via droplets, characterized by epidemic and pandemic spread, respiratory tract involvement, and prominent intoxication, fever, and moderate catarrhal symptoms.

Influenza is the most widespread infectious disease and a leading cause of temporary disability. It primarily affects the Respiratory system. Consequently, in the past—before its Etiology was fully understood—influenza was frequently mistaken for a common cold.

Influenza affects all segments of the population regardless of age, sex, or place of residence. It spreads in the form of epidemics, rapidly sweeping through a village, city, or country, or—over several months or even years—engulfing all continents, in which case it is referred to as an influenza pandemic (from the Greek "pan" meaning all, and "demos" meaning people).

In recent years, influenza epidemics have occurred annually, with the number of cases during an epidemic outbreak exceeding the total annual incidence of all other infectious diseases combined.

Historical manuscripts dating back to the 5th century BCE describe the sudden and rapid spread of a disease across multiple countries simultaneously, which was very likely influenza. The first mass outbreaks of respiratory illness recorded in 1173 CE, which rapidly swept through the populations of many European countries, can also be classified as an influenza pandemic.

During the Middle Ages, influenza pandemics recurred every 10 to 50 years, most of them exhibiting exceptional severity. The 19th century alone recorded 9 pandemics, and the 20th century saw 4. The disease spread rapidly across cities, countries, and continents, claiming millions of lives.

The most reliable historical accounts of past influenza pandemics point to the particularly devastating Nature of the 1889–1890 pandemic.

The first pandemic of the 20th century occurred in 1918–1920 and became known as the Spanish flu. Originating in China, it spread to the Americas and entered Europe via Spain. The disease propagated in waves. The first wave began in early 1918 and lasted for 6 months. While it infected a vast number of people, mortality was initially low. During the second wave, which erupted in the autumn of 1918, the disease took an extremely severe clinical course with a significantly higher mortality rate. Two additional waves swept through between 1918 and 1920, after which a 2.5-year lull followed with no pandemics or epidemics, although sporadic outbreaks continued to occur almost annually.

Approximately 500 million people contracted the Spanish flu, and 20 million lives were lost over the course of 2 years.

In the early years of Soviet rule, public health authorities faced the critical challenge of the "Spanish plague," prompting a decision to mobilize all medical resources of the young nation to combat the deadly disease.

In terms of spread and high mortality, the 1918–1920 pandemic was more dangerous than plague or cholera. The disease struck people indiscriminately regardless of age, yet children suffered particularly severe illness and high mortality.

Subsequent influenza pandemics occurred in 1947–1948, 1957–1959 ("Asian" flu), and 1968–1969; these originated in Southeast Asia and the Pacific coast. During each of these outbreaks, approximately 50% of the population contracted influenza in various countries. Much like the Spanish flu, the disease predominantly affected children. However, all of these subsequent pandemics were characterized by a milder clinical course and a more favorable prognosis than the Spanish flu.

Pandemic intervals were marked by periods of relative calm, punctuated by surges in morbidity such as influenza outbreaks and epidemics. Over time, non-epidemic years became increasingly rare. Recently (1970–1986), annual epidemics have affected 10–25% of the population, resulting in occasional fatalities.