Measles Rises From The Dead

The measles virus, thought to be eliminated in the United States, has come back in an outbreak, spurred by insufficient vaccination.

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By Maheen Rahman

Measles, a disease that has been considered eliminated in the United States since 2000, is coming back in droves across the country. So far in 2024, the number of measles cases is more than double the amount of cases reported in the entire year of 2023. Now you, as a student in New York City, have probably never had measles. Perhaps you heard about it from a parent or grandparent, or learned about it from your science teacher back in middle school. Most school systems require vaccination against measles, including the NYC DOE, and the vaccine has kept Stuyvesant students safe and healthy their entire lives. You probably don’t remember getting two shots against it as a baby. In fact, it may have been so long since you thought about the disease that you find yourself thinking: What even is measles?

Measles is considered one of the most contagious diseases in existence. It is so contagious, in fact, that a sick individual will infect nine out of 10 unimmunized people they come in contact with. It is an airborne virus, meaning that it spreads through respiratory droplets as an infected person coughs, sneezes, or breathes. The measles virus can live in the air for up to two hours. After contracting the virus, there is an incubation period of 10-14 days before symptoms appear as the virus spreads from the respiratory tract to the lymphoid tissue, where white blood cells are found. Then comes the prodromal, or early symptoms phase, marked by the onset of symptoms such as fever, runny nose, watery eyes, and cough. This is when the virus is most contagious due to the high viral load and lots of release of the virus into the air. About four days after the onset of the first symptoms, the signature measles rash develops, consisting of small red bumps that spread from the face to the trunk and the rest of the body over a period of several days.

Most people recover from measles within one to two weeks, but in some cases measles can also lead to complications, especially in patients who are under five or over 20 years old and have not been vaccinated, pregnant, or immunocompromised (having a compromised immune system).  These complications can range from ear infection and diarrhea to pneumonia, pregnancy complications, encephalitis (swelling of the brain) and even death in severe cases—about 0.1 percent of the time in the U.S. due to the high rate of effective vaccination, but up to 15 percent in less developed regions. The measles virus also directly attacks the lymphocytes, or the B and T cells of the immune system, and can reduce the amount of antibodies present in the body, thus reducing the body’s ability to fight back against infection. The virus’s genetic material can persist in these lymphoid tissues, leading to continued marked immunosuppression for years after the initial contraction of disease.

If the virus is so contagious, you may ask, then why are we just now seeing more cases?

The measles virus actually has a very effective and safe vaccine. The measles, mumps, and rubella vaccine (MMR vaccine) works similar to many others in that it contains a weakened form of the virus, known as the live attenuated virus, which is unable to cause illness but enough to stimulate the body’s immune system. When the body’s immune system recognizes the viral antigens (proteins that identify the virus) on the surface of measles, the B cells release measles-specific antibodies that bind to the virus to either neutralize them or mark them to be killed. The viruses are then dealt with by the two subsets of T cells: CD4+ (helper) T cells and CD8+ (cytotoxic) T cells. The helper T cells release cytokines (signaling proteins) that stimulate other immune cells, including B cells and cytotoxic T cells. Cytotoxic T cells recognize and eliminate cells that have been infected by the pathogen, preventing the spread of the infection within the body. Some B and T cells also differentiate into memory cells which help “remember” the pathogen and bring long-lasting immunity.  The MMR vaccine is given in two doses: the first at about one year of age and the second at around age five, after which the recipient is considered protected for life.

The MMR vaccine is incredibly effective not only because it allows the body to prepare its defenses against the real disease, but also because the measles virus does not mutate as much as other RNA viruses like influenza or COVID-19.  Though RNA viruses are generally more prone to mutations due to their lack of a proofreading system and rapid replication, the measles virus has a mutation rate of approximately 10-5 mutations per nucleotide per replication cycle, compared to influenza which has a mutation rate of closer to 10-3. This means that the measles virus does not change too significantly over time, and as a result, the immunization from the MMR vaccine is lifelong. The vaccine is so effective that both measles and rubella were declared eliminated in the U.S. in the year 2000. Prior to the introduction of the measles vaccine in 1963, measles was considered an endemic childhood illness—an illness that consistently and predictably presented in children—such as chicken pox or the flu. Annually, the disease infected approximately four million Americans, accounting for 450 to 500 deaths and thousands more with permanent disability.

So why, then, is measles coming back? The reigning theory is due to a lack of vaccination. During the peak of COVID-19, from 2020 to 2022, over 61 million doses of the MMR vaccine were not administered due to pandemic related delays in immunization activities. Also relevant is the rise in vaccine hesitancy, or the anti-vaxxing wave. As more people refuse vaccines like the MMR, more diseases previously considered eliminated can come back. The MMR vaccination rate in the U.S. has been steadily decreasing, from 95.2 percent in 2019-2020 to 93.1 percent in 2022-2023. The CDC and WHO declared that a vaccination rate of at least 95 percent is necessary for herd immunity, or the level of immunity within a community to protect those who are not immune. Now that the national average is below that level—and, in some states, the average is below 90 percent vaccination coverage—the virus can more easily move through a population and cause outbreaks like we are seeing throughout the nation.

In the late 1980s and early 1990s, the US experienced a similar phenomenon when a devastating measles outbreak hit and spread throughout the country due to a lack of vaccination and available healthcare services. In response to the outbreak, public health authorities implemented aggressive vaccination campaigns to increase measles immunization rates. This included targeted efforts to reach underserved communities and improve access to vaccines, as well as more available education about the benefits and safety of the vaccine. This event helped to bring awareness to healthcare and the importance of vaccination. Unfortunately now, we are repeating those same trends.

As of April 26, 2024, there have been 128 cases of measles in 20 states, which may not seem like a lot, but it is the steepest rise in measles cases since the outbreak of 2019, which was considered the highest concentration of cases in 25 years. On March 25, 2024, four cases of measles were reported, which again might not seem like a lot, but considering that the average number for the past four years has been zero and how fast measles can spread, it’s rather significant. If this trend continues, there is a concern that measles will lose its eliminated status and potentially return as an endemic disease.

As we move forward, it is important to remember the importance of vaccines and other preventative measures. While it may be easy to forget the danger of certain diseases as they get farther back in our memory, we must always consider what kept them back in the first place, and what is keeping them from returning. Measles is a very easily preventable virus, but it takes a community effort to keep it eliminated. Perhaps one day, the measles virus will join the ranks of the eradicated worldwide, alongside smallpox, and we can rest easy knowing that we will never have to worry about it again.