When germs appear, white blood cells have a variety of special tactics they can deploy to knock out the invaders. In some cases, they produce protective antibodies to overpower the germs. Other times, white blood cells surround and devour the bacteria. You might say that white blood cells live fast and die young.

During phagocytosis, a white blood cell encounters a microbe, engulfs it, and eats it. Once inside the cell, the microbe can be killed using a combination of degradative enzymes, highly reactive chemicals, and an acidic environment.

They flow through your bloodstream to fight viruses, bacteria, and other foreign invaders that threaten your health. When your body is in distress and a particular area is under attack, white blood cells rush in to help destroy the harmful substance and prevent illness. White blood cells are made in the bone marrow.

Your body shows signs of a strong immune system pretty often. One example is when you get a mosquito bite. The red, bumpy itch is a sign of your immune system at work. The flu or a cold is a typical example of your body failing to stop the germs/bacteria before they get in.

What are viral diseases?

• Chickenpox.
• Flu (influenza)
• Herpes.
• Human immunodeficiency virus (HIV/AIDS)
• Human papillomavirus (HPV)
• Infectious mononucleosis.
• Mumps, measles and rubella.
• Shingles.

COVID-19 is a disease caused by a virus called SARS-CoV-2.

The coronavirus outbreak has been labelled a pandemic by the World Health Organization (WHO). It is a term that the organisation had refrained from using before now. WHO chief Dr Tedros Adhanom Ghebreyesus said it was now using the term because of deep concern over “alarming levels of inaction” over the virus.

Viruses are responsible for causing many diseases, including:

• AIDS.
• Common cold.
• Ebola virus.
• Genital herpes.
• Influenza.
• Measles.
• Chickenpox and shingles.