After 31 years as a Navy doctor, I can’t get away from this analogy. Don’t take it too literally, but if you get infected with COVID-19 your body goes to war against the virus.
When the virus invades your body, it causes fever, loss of taste and smell, respiratory and other symptoms. We can think of the virus as the enemy. In response to this enemy invader, the body goes to war.
How would our country fight an enemy trying to do us harm? We would first respond by calling up the Marines! Marines are known as the “first to fight”. We have also heard that the Marines “run toward the sound of gunfire” to immediately engage the enemy in battle.
After the Marines get things under some control, the GI’s in the Army are not far behind. No offense to my Army buddies, but the Army has a different role in this example. The Army comes to the fight with different weapons and more refined machinery. It is able to mount a massive attack on the enemy at their weak points, and keep them from escaping to other places. The Army is “in it to win it”. It makes sure the enemy is eradicated.
Our body can’t call in the Marines or the Army, but it can make proteins called “antibodies” to fight the fight. We call this the “antibody response”. The most commonly known antibodies are IgM and IgG.
Like the Marines, IgM is the first antibody in the fight against the virus. It usually appears three to five days after an infection. It pins the invader down in their location and mounts a sustained attack. IgM has more primitive weaponry and usually has done all it can do in seven to fourteen to days. It leaves the battlefield and is usually not detected in a blood test after a month.
Meanwhile the Army has been gearing up. The body uses the protein antibody IgG for this role. IgG appears seven to fourteen days after the infection and stays for months. Like the Army, IgG has a better understanding of the enemy. It is more sophisticated and brings in more lethal weaponry to kill the virus. IgG continues to fight and clean up the infection in a big way for months. In that way, IgG makes sure the virus does not break out of the body’s defenses.
So whether it’s IgM responding like the Marines, or IgG doing their duty like the GI’s of the Army, we can be thankful our body can mount a defense against COVID-19 or any virus or bacteria. And in most all cases, we recover without any long term effects.