A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Blizzards can have an immense size and usually stretch to hundreds or thousands of kilometres. Definition and etymology
In the United States, the National Weather Service defines a blizzard as a severe snow storm characterized by strong winds causing blowing snow that results in low visibilities. The difference between a blizzard and a snowstorm is the strength of the wind, not the amount of snow. To be a blizzard, a snow storm must have sustained winds or frequent gusts that are greater than or equal to 56 km/h (35 mph) with blowing or drifting snow which reduces visibility to 400 m or 0.25 mi or less and must last for a prolonged period of time—typically three hours or more. Environment Canada defines a blizzard as a storm with wind speeds exceeding 40 km/h (25 mph) accompanied by visibility of 400 metres (0.25 mi) or less, resulting from snowfall, blowing snow, or a combination of the two. These conditions must persist for a period of at least four hours for the storm to be classified as a blizzard, except north of the arctic tree line, where that threshold is raised to six hours.
Neutropenia is considered chronic when it persists for more than 6 months. Signs and symptoms
Neutropenia, which may be discovered on routine blood tests, typically causes benign infections even when the condition is severe. Ear infections (otitis media) are the most common infection seen in autoimmune neutropenia and typically infection responds to antibiotic treatment alone. Infections associated with primary AIN are usually mild and limited, including skin infections such as impetigo, gastroenteritis, upper respiratory tract infections, and ear infections. Rarely, cellulitis and abscesses may occur. Studies of children studied for up to six years showed that most cases of autoimmune neutropenia resolved spontaneously after a median of 17 months. In 95 percent of patients, neutropenia persisted for 7 to 24 months. Diagnosis
The diagnosis of autoimmune neutropenia is based on blood tests demonstrating neutropenia and the presence of granulocyte-specific antibodies. In some cases, tests for granulocyte-specific antibodies must be repeated several times before a positive result is seen. Bone marrow aspiration, if performed, is typically normal or it can show increased cell production with a variably diminished number of segmented granulocytes.An association with prior parvovirus B19 has been made, but this hasn’t been confirmed. Treatment
Treatment consists of corticosteroids to reduce autoantibody production and antibiotics to prevent infection. Granulocyte colony-stimulating factor (G-CSF) is recommended to temporarily increase neutrophil counts in patients with absolute neutrophil counts (ANC) of less than 0.5 x 109/l and recurrent fever or infections.In cases of severe infection or the need for surgery, intravenous immunoglobulin therapy may be used.