When people hear the word “measles,” the first thing that may come to mind is a red rash. This distinct skin inflammation is definitely one symptom of the disease, but there are numerous others. And, alongside the typical signs of measles, the potential complications of the affliction are more dangerous than many people realize.
The measles vaccine (part of the two-dose measles, mumps, and rubella [MMR] vaccine administered to children) has resulted in massive decreases in cases worldwide. The immunization from the vaccine is lifelong, and if an individual has the measles, they are also immune to future infections (it is important to note that there are exceptions to both of these instances).
Measles does still exist, however, and the disease is still transmitted today. As a result, here’s a look at what measles actually does to the human body.
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Once It Enters The Body, The Measles Virus Incubates For Days Or Weeks
Measles is highly contagious and once the virus that causes it enters the body, it incubates for up to 12 days before symptoms appear. The measles or rubeola virus is transmitted by air or via bodily fluids.
Sneezes, coughs, and even talking can all transfer measles from one person to another. Touching someone with measles or a surface contaminated with the measles virus can also result in transmission. Because the measles virus stays active in the air for up to two hours, breathing near where someone with measles has talked or breathed similarly increases the risk of spreading the disease.
Once the virus is in the body, it spreads but there’s no indication that measles is present. As a result, outbreaks are possible in populations that are not protected. Travel is especially concerning to experts and the Centers for Disease Control recommends “all travelers are fully vaccinated against measles when traveling to any international destination” from the United States.
With increased numbers of Americans unvaccinated, domestic travel in the United States has become increasingly dangerous. In early 2025, one study,
estimated that a 10% relative decline in vaccine uptake because of greater vaccine hesitancy would increase the proportion of children and adolescents susceptible to measles from 13.5% to 21.4%.
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Initial Symptoms Include Fever, Cough, And Spots Inside The Mouth
The first symptoms of the measles resemble several other illnesses, including the flu and a cold. A fever that lasts for between four and seven days is accompanied by a cough, a runny nose, and red eyes – otherwise called conjunctivitis.
Another symptom of measles is the presence of Koplik’s spots. These are bluish white spots in one’s mouth. They resemble “grains of salt on a red background.”
Koplik’s spots are small and do not hurt, so they may go unnoticed. Not everyone with measles develops Koplik’s spots, but they usually appear one or two days before the more characteristic measles rash.
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It’s the most recognizable symptom of measles: the red rash that covers the body. When the rash first shows up, it’s usually near one’s hairline. From there, it spreads to the face, neck, and arms before running down the chest, back, and torso. Then, it descends the legs to the feet.
The measles rash is not painful but can be itchy. This explanation from Science offers a glimpse at what’s going on inside the body:
As the virus travels in the blood, it infects capillaries in the skin. Immune cells detect the infection and respond by releasing chemicals such as nitric oxide and histamines, which destroy the viral invaders and call other immune cells into action. These same chemicals, however, cause swelling and damage to host cells, resulting in the often itchy skin rash.
When the measles rash appears, one’s fever may spike to 104° Fahrenheit or higher.
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Potential Complications Of Measles Include Ear And Respiratory Infections And Diarrhea
Measles can lead to deadly complications because it invades one’s respiratory system before spreading to lymph nodes and into the bloodstream. Ultimately, the spread,
allows the virus to infect various organs and tissues, including the skin, the lining of the eyelids, and other epithelial surfaces. As those cells are destroyed, the combination of cell destruction and immune response lead to the symptoms of measles.
The damage to one’s body can be so extensive that it damages the lungs, skin, eyes, and digestive track. Bronchitis and pneumonia may develop, both potentially deadly diseases. If a person with the measles gets diarrhea, they are at risk of becoming dehydrated as well. One additional risk from measles is developing encephalitis, or swelling of the brain.
According to Dr. Adam Ratner, susceptibility to other infections can last for years after having measles, adding to the risks of the disease. This is because, as explained by the Johns Hopkins University Bloomberg School of Public Health,
Scientists have found that measles wipes out the body’s memory of bacteria and viruses. This weakens your immune system, making you more likely to get sick from other diseases. This effect can last for years.
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The Measles Vaccine Lowered Cases Of The Disease Worldwide, But It Isn’t Eliminated
According to infectious disease expert Dr. Daniel Kuritzkes,
During the time before vaccination, measles has a mortality of around 5% and in impoverished areas maybe 20% to 30%.
In the United States, the measles vaccine became widely available during the 1960s, and as a result, cases decreased significantly. Vaccination of children – individuals at high risk of getting measles – was successful to such an extent that the Centers for Disease Control said it hoped to eliminate measles by 1982. This didn’t happen, but in 2000, the US was declared free of the disease.
Worldwide, there’s less success in terms of eliminating measles infections because the vaccine is not as commonly administered. In 2023, the number of global measles cases increased by 20% from the previous year, with 10.3 million reported infections and 107,500 deaths. To then CDC Director Mandy Cohen, this was a call to act:
The number of measles infections is rising around the globe, endangering lives and health… The measles vaccine is our best protection against the virus, and we must continue to invest in efforts to increase access.
The resurgence of measles in some places like the US may be the result of the anti-vaccine movement but, as Dr. Adam Ratner pointed out in 2025:
The anti-vaccine movement or vaccine hesitancy has been around for as long as there have been vaccines. And so that part isn’t surprising. But what I think has happened is we’ve gone from a time where people realized that it was worth small amounts of risk for big amounts of gain, and the big amounts of gain were protection against these diseases.
