Measles in Mexico: Symptoms and How to Know if I'm Vaccinated

MÉRIDA.- Yucatán registered its first case of measles in 30 years , while in a few hours Chihuahua went from more than 700 confirmed infections to 922 – some already recovered -.

Given the current situation, Yucatecan specialists warn of the risk of a resurgence of the disease due to low childhood vaccination coverage and a decline in the practice of exclusive breastfeeding.

Although it is a highly contagious disease that had been practically eliminated in the country, cases began to rise in 2025 due to the apparent loss of vaccination culture.

Here we tell you the symptoms, treatment, and how to know if you've been vaccinated against measles in case of the possible threat of a resurgence.

Measles is a highly contagious disease caused by a virus that belongs to the paramyxoviridae family of the morbillivirus genus .

Humans are the only reservoir of the virus.

It can be acquired at any age, even in adulthood if a person did not suffer from it in childhood.

The Mexican Social Security Institute (IMSS) explains that it is spread through invisible droplets that come out of the nose and mouth of sick people, either through direct contact or through the air.

Infected droplets can remain in the air for about an hour. They can also land on a surface, where they remain active and spread for several hours.

From exposure to the disease until the first symptoms (such as fever) appear, it takes 10 to 12 days . From exposure to the appearance of the rash , it takes about 14 days, with a range of 7 to 18 days .

According to the IMSS , the first typical symptom is the appearance of fever , lasting at least three days, cough, runny nose, and conjunctivitis (red eyes).

Fever can reach 40°C, and in patients with a weakened immune system, pneumonia can develop.

Signs and symptoms of measles appear 10 to 14 days after exposure to the virus and include:

• Fever
• Hacking cough
• Runny nose
• Sore throat
• Inflamed eyes (conjunctivitis)
• Tiny white spots with a bluish-white center and a red background inside the mouth, on the inside of the cheek, also called Koplik spots
• Rash consisting of large, flat spots that usually merge into each other

Measles is a serious viral disease that can cause complications such as pneumonia, encephalitis , and in extreme cases, death .

Complications may include:

• Diarrhea and vomiting due to dehydration
• Bacterial ear infection
• Bronchitis, laryngitis, or inflammation of the airways (croup)
• Pneumonia, which can be fatal
• Encephalitis: in 1 in 1,000 people with measles
• Problems during pregnancy

There is no specific treatment for measles , and most patients recover within 2 to 3 weeks.

However, measles can cause serious complications , such as blindness, encephalitis, severe diarrhea, ear infections, and pneumonia, especially in malnourished children and immunosuppressed patients.

According to the World Health Organization (WHO), measles is one of the leading causes of death among children .

According to the Mayo Clinic , risk factors for measles include:

• Not being vaccinated
• Traveling to countries where infections are frequent
• Having vitamin A deficiency

The disease is especially serious in children under 5, adults over 20, and people with weakened immune systems (carriers of cancer, HIV-AIDS, malnutrition), explains the official Mexican government website.

Babies born to women who have received the vaccine or who are immune because they have already had measles are usually protected against measles for about 6 months after birth .

The IMSS emphasizes that the best protection against measles for children is the triple viral vaccine (which protects against measles, rubella, and mumps ).

In the case of adolescents and adults, it is the double viral (measles and rubella), as indicated by the Universal Vaccination Program .

The measles vaccine in Mexico is administered in two doses : one at 12 months of age or before turning 6 years old, and the other at 6 years of age or upon entering primary school.

Two doses of MMR (Measles, Mumps, and Rubella) represent almost 100% effectiveness in preventing measles , explained the IMSS.

If you haven't had the disease or been vaccinated, you may be exposed, so you should consult your doctor about whether you need to get the measles vaccine.

It is very important to know that the vaccine should not be administered during the first trimester of pregnancy, in the case of women.

This vaccine can be requested at the IMSS clinic where the beneficiary is affiliated, by presenting the vaccination record.

You can learn more about the Triple Viral (MMR) and Double Viral (MR) measles vaccines and their use in Mexico through the federal government's official website here .

It is possible, but very unlikely.

More than 93% of people who receive the first dose of the MMR vaccine develop immunity to measles . After the second dose, about 97% of people are protected, the Mayo Clinic explained.

Tests are now available to determine if you are immune (protected from infection) to measles because of vaccination or because you have contracted the disease in the past.

These tests are known by various names such as measles immunity test , measles blood test, measles virus culture , measles virus RT-PCR, IgM antibodies, anti-measles IgG, IgM antibodies…

Antibody tests require a blood sample. Molecular tests typically use a sample of blood or fluid from the mouth, throat, or nose.

A positive result means different things depending on the type of test:

• A positive molecular test result (PCR) means that measles virus was found in your sample, and that you currently have an infection.
• A positive IgM antibody test result means you currently have a measles infection or have recently had one.
• A positive IgG antibody test result means you are immune to measles either from vaccination or a previous infection.

The above according to the medical site Medline Plus here .

In Mexico , measles vaccines are part of the basic vaccination schedule, so you can verify their application by checking your National Health Card .

It is also possible to request information about vaccination history at public health centers if the record has been lost.

As of May 5, 2025, measles cases in Mexico totaled 789 .