Causes and Risk Factors of Meningitis

Meningitis is inflammation of the meninges, the tissue that covers and protects the brain and spinal cord. It is usually caused by an infection but may be caused by cancer, medication, or another inflammatory condition. When meningitis is caused by infection, it is usually bacterial or viral. The infectious causes of meningitis are contagious and spread by fluids that contain the infectious organisms. Sneezing, coughing, kissing, or even touching contaminated objects can spread the infection.

Common Causes

The causes of meningitis vary, although the most common causes are bacterial or viral infections, which you can catch by being around infected individuals through respiratory droplets. Other types of infections can occur as well, and they are more likely among people who do not have healthy immune systems, although infectious meningitis can affect anybody. 

Know, however, that although certain infections can cause meningitis, it is, in fact, an uncommon complication.

Bacterial Infection

There are several types of bacteria that cause meningitis. Each different type of bacteria is more likely to cause meningitis in a certain age group.

• Newborns: Group B Streptococcus, Streptococcus pneumoniae, Listeria monocytogenes, Escherichia coli
• Babies and children: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus
• Teens and young adults: Neisseria meningitidis, Streptococcus pneumoniae
• Older Adults: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus, Listeria monocytogenes

Tuberculosis meningitis is not necessarily associated with a particular age group, and it is an aggressive type of meningitis that can progress rapidly. 

Viral Infection

Viral meningitis can affect people of all ages, but children under the age of 5 and those whose immune systems have been weakened by disease, medication, or a transplant are at a higher risk. Infants younger than one month of age and people with weakened immune systems are also more likely to have a severe case of meningitis when they do get it.

The most common causes of viral meningitis are:

• Enterovirus
• Mumps
• Measles
• Influenza virus
• Herpes simplex virus
• Varicella zoster (the virus that causes chickenpox)

Fungal and Parasitic Meningitis

While less common than bacterial or viral cases, meningitis can be caused by fungal and parasitic infections, particularly among people who do not have a healthy immune system. 

Chemical Meningitis

Meningitis can be caused by an inflammatory reaction to certain medications and procedures. For example, a number of antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs) have been associated with aseptic meningitis, meaning meningitis that is not infectious. Sometimes neurosurgical procedures or a lumbar puncture can cause aseptic meningitis, although it is very uncommon. 

Cancer

Cancer metastasis (spread) from elsewhere in the body can travel to the meninges. Cancer cells that invade the meninges may cause an inflammatory reaction, with severe neurological symptoms and potentially lasting effects. 

Autoimmune Disorders

A number of autoimmune disorders, including lupus and sarcoidosis, have been linked to inflammatory meningitis. In these instances, symptoms of meningitis occur and inflammation is present, but there is no identified infectious organism, and the illness may improve with immunosuppressant medications.

Health Risk Factors

Infectious meningitis is influenced by several factors related to your overall health:

Age

Certain age groups are at a higher risk of becoming infected with meningitis:

Maternal Transmission

Maternal to infant transmission can develop if the mother has an infection of the birth canal that could cause meningitis in the newborn child, such as herpes. 

Immune Deficiency

People who do not have a healthy immune system are at a higher risk of getting infectious meningitis. An immune deficiency can occur due to immunosuppressant medications, chemotherapy, or any illness that affects the immune system, such as HIV or lupus. 

STD Status

There are several sexually transmitted diseases that can lead to meningitis. For example, advanced syphilis infection can become meningitis. HIV infection, which is sexually transmitted, can suppress the immune system, making it more likely for an infection to become meningitis. 

Lifestyle Risk Factors

A number of lifestyle risk factors have been associated with meningitis risk. While removing yourself from these settings may not always be possible, you can take extra precautions to stay safe if there's a known case of meningitis (even if you've been vaccinated against it).

Attending School

School-age children, young children who go to daycare, and their teachers are all at risk of meningitis due to their close proximity to one another during the day. Shared utensils and other items can increase the spread of infection.  

Living in a Shared Residence

College student dorm life, which involves sharing living spaces with many other people, increases the risk of meningitis. Similarly, camping groups and sports teams that travel together are also at risk of getting meningitis. 

Working With Animals

Zoonotic meningitis affects people who work or play extensively with animals, as well as people who live in areas where the bacteria can be found in animals.

Traveling

Traveling may increase your risk for meningococcal disease. Exposure to infectious organisms that you have not ever been exposed to, such as tuberculosis, for example, is more likely if you travel to a region where the infection is more likely. This can put you at an increased risk of developing meningitis. 

Being Unvaccinated

If you aren't up to date on your recommended vaccines, you will be more susceptible to infections from certain types of bacteria and viruses.