Delhi High Court directed the National Centre for Disease Control (NCDC) to submit a report and analysis of the serological survey that was recently conducted in the national capital

It has been observed that SARS-CoV-2 causes asymptomatic infection for which sero- surveillance is strongly recommended for active case finding, testing, and contact tracing.

Also, surveillance of antibody based sero-positivity indicates the extent of spread of infection in the given population and forms the basis for strengthening public health mitigation measures

Serosurveillance provides estimates of antibody levels against infectious diseases and is considered the gold standard for measuring population immunity due to past infection or vaccination.

The blood samples are tested for detecting IgG antibodies. The IgG antibodies generally start appearing after two weeks of onset of infection, once the individual has recovered after infection and last for several months. Therefore, the IgG test is not useful for detecting acute infection but indicates episode of Sars-CoV2 infection in the past

The presence of IgM, which withers away in days, in a blood sample indicates a recent infection. The presence of IgG antibodies suggests a relatively older infection.

Plasma

 The liquid part of the blood and lymphatic fluid, which makes up about half of the volume of blood. Plasma is devoid of cells and, unlike serum, has not clotted. Blood plasma contains antibodies and other proteins. It is taken from donors and made into medications for a variety of blood-related conditions.

Antibody

A protein, an immunoglobulin, made by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response). Each antibody can bind to only one specific antigen. The purpose of this binding is to help destroy the antigen.

The production of antibodies is a major function of the immune system and is carried out by a type of white blood cell called a B cell (B lymphocyte). Antibodies can be triggered by and directed at foreign proteins, microorganisms, or toxins. Some antibodies are autoantibodies and home in against our own tissues.