Acute Brain Infections: Breakthroughs in Management

“[Bacterial meningitis] is terrifying because it happens very fast—within 24 hours you can develop a high fever and then die. And it is not only young babies that are affected, but children, adolescents and young adults.”

Dr. Marie-Pierre Preziosi, epidemiologist, head of WHO initiative Defeating Meningitis by 2030.

“Treatment without prevention is simply unsustainable.”

Bill Gates, American philanthropist, Microsoft cofounder

Very few infectious diseases capture as much attention as those involving the brain, in particular acute bacterial meningitis and viral encephalitis. Globally, bacterial meningitis causes an estimated 236,000 deaths annually, and an estimated 89,000 people die from encephalitis each year. Remarkable breakthroughs in the diagnosis, treatment, and prevention of these infections have occurred, but many such advances aren’t recognized by the general public. In this week’s Germ Gems post, I highlight some of the breakthroughs that have occurred in this field over the course of my career.

Overview of central nervous system (CNS) infections. Conceptually, the brain is both a highly complex and prized organ. Many scientists consider the brain an immunologically privileged site, meaning the brain has mechanisms that not only prevent access of foreign invaders, that is, microbes, but also minimize damage caused by immune responses. (For a discussion of this topic, see, “What’s Bugging the Brain?,” Germ Gems, February 22, 2023).

Despite being an immunologically privileged site, a myriad of microbes (bacteria, viruses, fungi, and parasites) evolved workarounds to gain entry into the CNS where they wreak havoc. For the purposes of this Germ Gems post, I consider only two types of acute CNS infections: bacterial meningitis and viral encephalitis.

What is acute bacterial meningitis? Meningitis refers to inflammation of the tissues surrounding the brain and spinal cord (the meninges). The bacteria that can cause bacterial meningitis include Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. In its April 1, 2025 overview of bacterial meningitis, the World Health Organization (WHO) points out that around 1 in 6 people who get this infection die, and 1 in 5 suffer severe complications. (At age 19 months, Helen Keller contracted bacterial meningitis caused by N. meningitidis or H. influenzaeand while she is the most famous American to survive this bacterial infection, she was left deaf and blind.)

The most common symptoms and signs of meningitis are fever, neck stiffness, confusion, headache, and sensitivity to light (photophobia). Prompt administration of antibiotics that target the offending bacterium is perhaps the biggest breakthrough in the management of bacterial meningitis.

For community-acquired bacterial meningitis, the early institution of antibiotics is associated with optimal clinical outcomes, that is, reduced mortality and decreased complications such as blindness and deafness. And thanks to the pioneering research of pediatric infectious diseases specialist Carol J. Barker, aka “the Godmother for group B Strep prevention,” group B Streptococcal (GBS) meningitis has declined in neonates due to the implementation of intrapartum antibiotic prophylaxis for pregnant women who are colonized with GBS.

While antibiotics are “perhaps” the biggest breakthrough in the management of bacterial meningitis, one cannot ignore the enormous impact of vaccines in preventing acute bacterial meningitis altogether, specifically the H. influenzae conjugate vaccine, meningococcal vaccines, such as MenAfriVac, and the pneumococcal conjugate vaccine.

When I embarked on my career in infectious diseases about 50 years ago, H. influenzae was the most common cause of bacterial meningitis in children under five years of age. The introduction of the H. influenzae conjugate vaccine in 1987 was essentially the end of the road for this cause of meningitis in the developed world.

Another victory for vaccines in the management of bacterial meningitis is the introduction of MenAfriVac, a meningococcal group A vaccine that has had an enormous impact on reducing the incidence of group A meningococcal disease in the so-called “African meningitis belt,” a region in sub-Saharan African extending from Senegal to Ethiopia where the incidence of meningitis is very high.

The surveillance data show that the incidence of suspected meningitis cases declined by 57% in vaccinated compared to unvaccinated populations, and the incidence of confirmed group A meningococcal disease was reduced by more that 99%. According to the WHO, MenAfriVac has virtually eliminated this disease from a region that reported more than 150,000 deaths due to meningitis epidemics. (Historically, this region experienced major meningitis epidemics every 5 to 12 years where the attack rates could reach 1,000 cases per 100,000 population.)

And, finally, there are the pneumococcal conjugate vaccines. Beginning in 2000, pneumococcal conjugate vaccines began to be used widely leading to a marked reduction in pneumococcal meningitis cases, an infection that crosses various age groups.

What is viral encephalitis? Viral encephalitis is a serious condition where the CNS becomes inflamed due to viral infection. It can be caused by a variety of viruses, including herpes simplex virus (HSV), measles virus, and arboviruses such as the West Nile virus. Symptoms range from mild flu-like illness to fulminant neurological conditions, including seizures and loss of consciousness.

The severity of disease is determined by the nature of the infecting virus and the immunological reaction to it within the CNS. Although many offending viruses precipitate a relatively mild illness, at the other end of the disease severity spectrum is the rabies virus, one of the only pathogens that causes close to 100% mortality. Moreover, unlike bacterial meningitis, for which a variety of effective antibiotics exist, with the exception of HSV encephalitis, there are no specific antiviral drugs that are effective in treating viral encephalitis.

While not all viral encephalitis is preventable by vaccination, there are several vaccines that help prevent encephalitis caused by specific viruses. These include the measles, mumps and rubella vaccine, the varicella (chicken pox) vaccine, and most notably the rabies vaccine, which was discovered in 1885 by Louis Pasteur, the father of immunology and is estimated to save more than 250,000 human lives annually.

Is there a future for scientific research in the U.S.? Recently, there have been several breakthroughs in managing acute brain infections, especially in low- and middle-income countries. Many of these advancements are integrated into what is described as an “Intervention Package.” Such “intervention packages” involve a combination of improved diagnostics and advanced treatment guidelines tailored for each setting and include a diagnostic and management algorithm, a lumbar puncture pack, a testing panel and staff training.  (See,  “A multifaceted intervention to improve diagnosis and early management of hospitalized patients with suspected acute brain infections in Brazil, India, and Malawi: an international multicentre intervention study,” The Lancet, March 23, 2025, and “Another step towards defeating meningitis,” TheLancet, March 25, 2025.) This particular breakthrough could go a long way toward decreasing the burden of acute brain infections in the most affected regions of the world. But it is still unlikely that the WHO’s objective of defeating meningitis by 2030 will be met, and, sadly, it appears that the U.S. may provide little or no help.

A war against science is being waged in the U.S. and, at the moment, it appears science may be losing. Questions like“Will US science survive Trump 2.0?”, posed in the April 29, 2025 issue of Nature are mindboggling. And equally baffling is this report by CBS News in February 2025, “RFJ Jr. has raised doubts about vaccines, but data shows how many lives they’ve saved.” But, as the editors of The Lancet recently wrote: “The pursuit of rigorous medical science is not compatible with capitulation to government demands aimed at weaponizing and eroding science.” (See, “Supporting medical science in the USA,” The Lancet, April 26, 2025).

For those of us who have witnessed the remarkable scientific and clinical breakthroughs in the management of acute brain infections (as well as other infections) over the past 50 plus years, we can’t believe this is happening. The pathogenesis of this problem seems clear—mixing uninformed politics with science. The solution—returning to our senses—is a challenge, but just as Louis Pasteur and other scientists have shown, it’s not unsurmountable.