Deadliest Viruses Are Coming Back, Here’s Why

Previously controlled diseases like yellow fever, meningitis, diphtheria, tetanus, hepatitis B, measles, mumps, rubella, polio, and even the plague are re-emerging globally due to declining vaccination rates and public health infrastructure breakdowns.

• Deadly diseases are resurfacing due to declining vaccination rates and public health system breakdowns.

• Vaccination provides crucial, often lifelong, protection against infections with high fatality rates and severe complications.

• Maintaining widespread immunization and public health vigilance is essential to prevent future epidemics.

Despite significant progress through vaccination campaigns since the late 18th century, several deadly diseases are making a concerning comeback. These re-emerging threats, including bacterial and viral infections, pose a serious risk to public health, especially in areas with low immunization rates or disrupted healthcare systems. Maintaining high vaccination coverage is crucial to prevent widespread outbreaks and avert historical mortality rates.

Re-emerging Yellow Fever

• 00:00:19 Yellow fever, a mosquito-borne disease prevalent in Africa, South America, Central America, and the Caribbean, is re-emerging despite the existence of a single-dose, lifelong vaccine. Initial symptoms like fever and muscle pain are short-lived, but 15% of cases progress to severe forms involving liver damage, internal bleeding, and kidney complications, with a 50% fatality rate among severe cases. In 2024, Africa reported 124 cases across 12 countries, and the Americas are tracking 131 cases, highlighting the need for widespread immunization as no specific treatment exists.

• 00:02:16 Yellow fever, which can be fatal in about half of severe cases, lacks specific treatment, meaning only symptom management is possible once contracted. Despite a safe and effective vaccine offering lifelong protection with just one dose, cases are on the rise in various regions. Efforts to control the Aedes aegypti mosquito population are underway, but widespread immunization remains the primary defense against potential outbreaks.

Meningitis and Diphtheria Resurgence

• 00:02:37 Meningitis, particularly the bacterial form, rapidly attacks the brain and spinal cord membranes, causing swelling that can lead to brain damage, seizures, paralysis, and death within hours. While the Hib vaccine dramatically reduced cases, especially in children, stopping immunization could cause a dramatic spike in invasive Hib disease and deaths. Diphtheria, caused by Corynebacterium diphtheriae, produces toxins affecting the heart and nerves, with a 5-10% fatality rate that can rise to 20% in vulnerable populations; severe cases cause throat patches that can block airways. After the collapse of the Soviet Union, a diphtheria epidemic saw over 150,000 cases and 5,000 deaths, demonstrating the catastrophic consequences of lapsed vaccination programs.

• 00:05:06 Diphtheria, caused by toxins that can lead to major heart and nerve problems, has a fatality rate of 5-10%, increasing to 20% for the young or elderly. Symptoms begin with a sore throat and fever but can progress to severe infections causing gray or white patches in the throat that may block airways, alongside enlarged lymph nodes and swelling of the neck. Unlike many diseases, previous diphtheria infection does not guarantee immunity, making vaccination, which provides the necessary antitoxin, the only reliable protection against reinfection and a critical defense against its re-emergence.

Tetanus and Hepatitis B

• 00:07:57 Tetanus, caused by highly resistant bacteria found in soil and animal waste, can lead to muscle spasms severe enough to fracture bones, jaw locking, and throat closure, making breathing and eating difficult; about 1 in 10 cases are fatal. Although a vaccine introduced in 1938 drastically reduced cases, tetanus is resurging in the US, particularly among intravenous drug users and unvaccinated newborns whose mothers were not immunized. Hepatitis B, which infects over 2 billion people globally and leaves 350 million lifelong carriers, annually kills over a million people from liver disease and cancer.

• 00:09:33 Hepatitis B is transmitted through bodily fluids and can be passed from mother to baby during birth; an estimated 1,600 to 20,000 infected women in the US give birth annually. Approximately 1.25 million Americans have chronic Hepatitis B, with 20% acquiring it in childhood, and a quarter of these children are expected to die from liver disease as adults. Individuals taking immunosuppressant medication, those with HIV, or undergoing dialysis are at higher risk, underscoring the broad vulnerability to this widespread and severe viral infection.

Measles, Mumps, Rubella, Polio, and Plague

• 00:10:42 Measles, mumps, and rubella (MMR) are significant threats to children, preventable by a single vaccine. Measles, once a common childhood illness, caused 450 deaths annually before vaccination and still results in hospitalization and complications like pneumonia, the leading cause of measles-related deaths. Mumps can cause painful swelling of the jaw, cheeks, and testicles, and before vaccination, was the leading cause of childhood deafness. Rubella, or German measles, is particularly dangerous during pregnancy, causing congenital rubella syndrome (CRS) with severe defects like heart issues, cataracts, deafness, miscarriages, and neonatal deaths, as seen in the 1964-1965 epidemic. Disrupted immunization programs have led to a resurgence of measles, with nearly 1,400 confirmed cases across 41 US states in 2025.

• 00:15:22 Polio, which causes acute paralysis and historically crippled thousands, persists endemically in Pakistan and Afghanistan, despite successful global vaccination campaigns that eliminated it from many regions. Stopping vaccination before full eradication would guarantee a resurgence, threatening millions with the paralytic virus. The plague, including pneumonic, septicemic, and bubonic forms, is also making a comeback; though treatable with modern antibiotics, it has up to a 90% fatality rate without early intervention. Cases are still reported in the US and globally, highlighting the danger of declining vaccination and public health vigilance.

• 00:19:07 Vaccination against the plague is not routinely recommended but may become necessary for a wider population if cases continue to rise. Recent incidents in August 2025 saw a 43-year-old man hospitalized with bubonic plague in New Mexico, likely exposed to infected fleas while camping, and a man in Arizona died from the disease in July. Health officials urge preventative measures such as avoiding sick rodents, using insecticides, and treating pets, emphasizing that a halt to vaccinations could lead to an 'unwanted sequel to the Black Death'.