Meningitis is a dangerous disease that can lead to severe consequences and even death. Unfortunately, it also has a lot of causes and many types that make it more likely to get one of these. You can get bacterial meningitis, viral meningitis, fungal meningitis, parasitic meningitis, amebic meningitis or even noninfectious meningitis.
This is the case because the word meningitis is very broad and does include a lot of subtypes. The word “Meningitis” is composed of the first part “meninges,” which refers to the surrounding layers around the brain tissue. The suffix “itis” refers to inflammation, and it is the presence of inflammatory cells for any particular reason. Because the word is very broad as you can see, this allows for many subtypes, which makes determining the diagnosis very challenging and increases the number of ways by which you can get meningitis.
Although bacterial meningitis is not the most common form, it is still of great importance to understand how you can get it. Bacterial meningitis is fatal and can cause death in a short period of time. What makes bacterial meningitis more dangerous is that it can be caused by many strains of bacteria that can reach the surrounding layers of the brain in many ways we will talk about. The most common types of bacteria that can cause meningitis are Streptococcus pneumonia, Neisseria meningitides, Haemophilus influenza, and Listeria monocytogenes.
Streptococcus pneumonia is the most common cause of meningitis, especially in young people who include: children, teenagers. It is very common to get bacterial meningitis caused by streptococcus pneumonia because streptococcus pneumonia is a common bacteria that is present in your respiratory tract, which includes your nose and the part of the pharynx called nasopharynx. The percentage of carriers (the carriers are the people who have the bacteria but don’t show any sign of illness, but they can infect others and can’t be easily detected) of this bacteria in their nasopharynx is very high in young people. This is why it is more common to cause bacterial meningitis for them compared to adults.
Streptococcus pneumonia is present in only 5-10% of the adult population where it can reach up to 60% in children, which makes it clear why it is more common in this subcategory of the population. What makes infection with streptococcus pneumonia even more dangerous is its way of transmission from person to person. Streptococcus pneumonia can spread by direct contact, and this means that you can get infected by merely being near someone who has this specific type of bacteria. This is what makes this type of bacterial meningitis very dangerous as it is very contagious and can spread before noticing. Thus, many countries focus on its prevention and have particular protocols to start immediately if there is a suspected case.
What makes it even worse is that infection can happen by autoinoculation. Autoinoculation means that you infect yourself! You may be wondering how this can happen? Humans carry a lot of bacteria on their skins, in their guts, in their respiratory tract and other parts, as it is the case for streptococcus pneumonia. Some of those bacteria are beneficial, others are neutral, and a number of them can be infectious under the right condition. This takes us to an important concept in the epidemiology of any disease which is called the epidemiological triad.
Epidemiological triad refers to the three conditions that are required to cause an infection and they are: susceptible host (human or animal who is weak enough to allow for the infection to occur), suitable environment (the condition of the place where the bacteria or the infectious agent can thrive at) and finally the external agent (the bacteria, virus or fungus that can cause the specific type of this infection).
The interplay between these three elements is crucial in the process of infection. Because of all of this autoinoculation can occur in this type of infection, the person can become diseased after being a carrier. Thus, this person will be in imminent danger as if carrying an explosive bomb that can literally kill him and others around him, but he is not aware of this silent bomb and can’t take the precautions to prevent danger.
There are also other factors that, in general, contribute to the transmission of these bacteria, including being in a crowded area, certain seasons, and the presence of upper respiratory infections or pneumococcal disease. Fortunately enough, there is an available vaccine for this bacteria.
Neisseria meningitidis is another bacteria that can cause bacterial meningitis. Neisseria meningitidis is also known as meningococcal bacteria. It shares many features with streptococcus pneumonia as it is also present in the respiratory tract, whether it is the nose or the back of the throat and can also cause the state of being the carrier.
It has many subtypes, but the most common are: A, B, C, W, X, and Y. the infection by this bacteria can also happen as we have seen with streptococcus pneumonia. Direct contact with droplets of the respiratory tract or the saliva is one of many forms of infection, which can occur when you are in close contact with someone who has the bacteria in his respiratory tract or throat.
If you are in close contact with someone who has been known to have bacterial meningitis, you probably need to receive a dose of antibiotics to ensure you are protected. You can be relieved to know that this bacteria is not as contagious as viruses that can cause the common cold. There’s a vaccine against this bacteria as well, which is why we should all take some of our time to thank the people who work day and night to conquer those diseases.
Haemophilus influenza is less common than the previously mentioned bacteria. Nevertheless, it can still cause bacterial meningitis if you get infected. Haemophilus influenza is not limited to cause only meningitis; it can also cause a wide variety of infections from the simplest and self-resolving ones like mild ear infection to the fatal ones that can kill you like bacterial meningitis. This bacteria may also live normally in your respiratory tract, and in this case, you can get infected just in the same way as the previous bacteria.
This bacteria is weaker than the previous one and infects people with low immunity. Those people are commonly elders above 65 years old and children below 5 years. Those 2 subtypes of the population are always susceptible to uncommon types of infection that a fully functioning immune system can deal with. Knowing about this infection is crucial for doctors because it can guide them to act appropriately and eliminate this cause of bacterial meningitis quickly from their list of differential diagnosis when they are facing adults who aren’t old enough or young enough to have bacterial meningitis that is caused by Haemophilus influenza.
Listeria monocytogenes is yet another bacteria that is known to cause bacterial meningitis. It is so common that some papers estimate that it is the 3rd most frequent cause of bacterial meningitis. This bacteria has a particular way of transmission unlike the previous types of bacteria. Listeria monocytogenes can spread through food, which was discovered in an outbreak in the 1980s. It is a unique method of affecting the brain, yet it is accurate and proven that you can infect the outer coverings of your brain by eating contaminated food with Listeria monocytogenes.
This type of infection is common in the immunocompromised individuals, just like Haemophilus influenza is more common in the elderly. This is unfortunate for those individuals because Listeria monocytogenes in this population have high fatality rates that can reach up to 62%. This means that for every 100 people infected with Listeria monocytogenes, 62 will die from it.
Viral meningitis causes
Let us dive into the most common cause of meningitis which is viral meningitis. The great news is that this type of meningitis is less severe than bacterial meningitis. Nevertheless, it is still fatal. Many viruses can cause viral meningitis, but the most common types are non-polio enteroviruses.
You can consider viral meningitis to be seasonal as it is more common in late spring to fall. Be aware that you can be infected by any one of those viruses and not get viral meningitis. Actually not getting meningitis by those viruses is the almost always the case. Still, viral meningitis can happen, especially in people who have a problem or defect in their immunity and the degree to which their immune system is compromised determines the severity of the disease. Like most of the common causes of bacterial meningitis, viral meningitis requires close contact with the infected person to get the virus and it is important to remember the epidemiological triad which determines whether or not you will get meningitis or the infection will pass with no harm on you.
Fungal meningitis causes
Fungal meningitis is yet another type of meningitis. Despite the rarity, it is even more fatal, and that’s because we don’t actually have suitable treatments for fungal meningeal infections. So, we can feel relieved to know it is infrequent and also almost always accompanied by another condition that causes weakness in the immunity. HIV infection, cancer, steroid drugs intake or immune suppressant drugs intake are commonly present in the medical history of these patients.
Fungal spores are widely spread around us, and in the air we breathe. In most cases, there is no fear as your immune system cells are always there for you. But when they are affected by any cause, those spores will suddenly take advantage of the situation, and you will start to see the other ugly side of nature.
The most common fungus that can cause fungal meningitis is Cryptococcus, Histoplasma, Blastomyces, Coccidioides, and Candida. It is also important to note that, different from bacterial and viral meningitis, fungal meningitis is not infectious by the same means.
Parasitic meningitis (eosinophilic meningitis) causes
Parasitic meningitis is a rare type of meningitis aso known as eosinophilic meningitis because the most involved immune cell to fight off parasites are called eosinophils. Thus, under the microscope when you are checking a sample you will find a lot of them.
You can get this type by eating infected animals with the parasite, so you can’t directly get the disease as those types of parasite don’t infect humans. The most common parasites are angiostrongylus cantonensis, Baylisascaris procyonis, and Gnathostoma spinigerum. Those parasites are easy to avoid with enough hygienic consideration.
For example, Baylisascaris procyonis is associated with raccoon feces, so if you don’t get involved with dirt that is contaminated with raccoon feces you will be fine. Other types are involved with eating raw or undercooked snails and fish. So your next trip to Hawaii or japan, make sure not to eat what is not touched by enough fire.
Amebic meningitis causes
Amebic Meningitis is also a rare type of meningitis you can get by being infected with Naegleria fowleri. This particular type of meningitis is fatal very quickly, but fortunately, you can avoid this infection by not swimming in warm freshwater or, if you have to, make sure to protect your nose because it is the main gateway for the infection. Naegleria fowleri doesn’t live in saltwater, so you have all the oceans and seas to swim in. It is worth noting that drinking water that is contaminated with Naegleria fowleri doesn’t cause an infection.
Other non-infectious causes can lead to meningitis. With this type of meningitis, the spread is not possible, and the disease is confined to the patient only. These causes include cancer, systemic lupus erythematosus (SLE) and brain surgery.