FAQ About Measles Outbreaks Answered: What You Should Know

Since the start of 2024, four states have reported measles cases. Although measles outbreaks in the U.S. happen every year, the recent outbreaks have prompted some concerning headlines. How many cases occur each year, and how serious is the disease? We answer that and more.

What is measles?

Measles is a highly contagious viral illness, which was considered eliminated from the U.S. in 2000. However, cases are still imported when under-vaccinated travelers are exposed and return home.

Measles can be serious for babies and very young children as well as adults over 20 years of age because it can cause complications like pneumonia or encephalitis, requiring hospitalization. Measles infection can also cause serious complications if contracted during pregnancy.

What are the symptoms and how does it spread?

The symptoms of measles include high fever, cough, a runny nose, and watery eyes. A measles rash appears 3–5 days after the first symptoms. The rash first appears on the head as flat red spots near the hairline, then spreads down the body, from the trunk to the arms and legs. While the rash may appear red or brown on white skin, it may be harder to see on darker skin. The fever may spike as high as 104ºF during the rash phase of the illness.

The incubation period is 7–14 days, during which time a person is infectious even though they have no symptoms. The virus is spread through the air and is very contagious. Nine out of 10 people exposed will become infected, even hours after the first infected person leaves the room. A person is considered infectious from 4 days prior to the rash through 4 days after the rash appears.

How effective is the vaccine?

A highly effective vaccine is part of the routine childhood immunization schedule and protects against measles, mumps, and rubella. The first dose is recommended at 12–15 months of age, and the second at 4–6 years of age. If you are planning to travel, ask your doctor about getting an early dose of the measles vaccine, available to infants 6–11 months of age.

What can be done to prevent measles infection?

While infection is difficult to prevent if exposed because the virus is airborne, there is a difference between infection and illness. Infection means the virus enters your body and replicates in your cells. Illness is the symptoms you develop after infection. The best defense is a good offense — get vaccinated. When you are immune, you may be infected but do not get ill.

If you are already vaccinated, your odds of developing illness are dramatically reduced. This is because the vaccine presents a weaker version of the virus to your body and stimulates the production of antibodies and memory T cells. These antibodies can bind to measles if you become infected, while the memory T cells detect infected cells and destroy them, preventing further replication.

What else can you do to protect yourself against measles or any other virus circulating right now?

  1. If you are not fully vaccinated, talk to your doctor about any vaccines you might have missed during the pandemic.
  2. Use good hand hygiene by washing with soap and water and stay home if sick to avoid spreading infection.
  3. Get enough sleep and exercise to allow your body to repair and promote good circulation.
  4. Eat a well-balanced diet rich in pre- and pro-biotics to boost immunity and ensure a steady supply of micronutrients.
  5. Get adequate hydration to make sure your immune cells can navigate freely to fight off pathogens.

Why are two doses of vaccine necessary?

One dose of measles vaccine prevents 93% of cases, and a second dose prevents 97% of cases. Two doses are recommended because a small percentage of the population does not respond to a single dose. Covering the entire population with a two-dose series brings the level of immunity high enough that imported cases do not cause widespread outbreaks.

How fast does the vaccine work?

You will start building immunity immediately upon receipt of the vaccine because your body recognizes the weakened form of the virus as a pathogen. After the initial response by generalist defenders, measles-specific antibodies will climb steadily over the next 2–4 weeks.

Are there side effects to vaccination?

Yes, any vaccine has side effects, but infectious disease experts are adamant that side effects are more tolerable than a measles infection due to the potential for serious complications to the disease. The most common vaccine-related side effects are a sore arm, fever, mild rash, pain or stiffness in the joints, and a minimal risk of febrile seizures or an allergic reaction.

What if I have measles?

If you have measles, stay home until at least four days after the rash appears. Use a tissue to wipe your nose and throw it away, avoid sharing utensils, wash your hands with soap and water frequently, and use standard household cleaners to wipe down high-contact surfaces.

What if a family member has measles?

Because measles is airborne, taking these precautions at home may not appreciably reduce the likelihood of transmission if others in the household are unvaccinated.

Take special precautions, such as carefully isolating away from others and using fresh air ventilation as much as possible if someone in your household is immune-compromised or too young to be vaccinated.

I am pregnant. How serious is measles?

Measles does not cause congenital disabilities, but complications can include miscarriage, low birth weight, stillbirth, and pre-term delivery. If you have not previously been vaccinated and plan to conceive, talk to your OB-GYN about the best timing for measles, mumps, and rubella (MMR) vaccination. The MMR vaccine is a live, attenuated virus vaccine and is not recommended during pregnancy.

How common is measles in the U.S.?

The highest number of cases since 2000 was in 2019, when 1,274 cases were reported to the CDC. In a typical year, the range of cases reported can be as low as 55 or as high as 667. The majority of cases are among under-vaccinated people living in close-knit communities.

Why is this outbreak happening now?

Measles outbreaks happen when new cases arise either due to exposures while traveling or within communities that have low vaccination rates. High vaccination rates help to build a “wall” of immunity, containing the outbreak. However, the pandemic caused more people to miss doses of MMR vaccine — the CDC estimates that 61 million doses were missed.

Measles outbreaks happen every year in the U.S., with some years experiencing higher numbers than others. Just before the pandemic, the U.S. experienced the highest number of measles cases in nearly two decades. All the 2019 U.S. outbreaks were connected to travel-related cases brought back to under-immunized communities.

The CDC reports that 71% of people infected in the 2019 outbreaks were unvaccinated, and the remainder either had an unknown vaccination status or only received one dose.

What if I am traveling this spring?

If you plan to travel overseas, check the CDC’s Travel Health Notices and ask your doctor about any vaccines you should consider before departure. Note that some vaccines need several doses for full coverage, so you may need to plan weeks to months in advance.

Measles was once a common childhood illness, but serious measles cases have declined dramatically with vaccination. When measles cases increase overseas, we can expect more exposure among travelers. Given that the CDC estimates over 60 million vaccine doses were missed during the pandemic, we can expect to see outbreaks in the U.S. this year among communities with low vaccination rates.

The best defense is to ensure your family is protected through vaccination. This is particularly important if anyone in your family is too young to be vaccinated (infants younger than a year) or has an immune-compromising condition that prevents them from receiving a live, attenuated vaccine like MMR.

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