In August 2025, the Pan American Health Organization (PAHO) issued an alert after noting a 34-fold increase in the number of measles cases compared to 2024. Ten countries in the Americas reported cases of the disease, totaling more than 10 confirmed cases and 18 deaths. Deaths were concentrated in Mexico (14), the United States (3), and Canada (1).
In Brazil, the most recent records indicate 24 cases by the end of August, 19 of them in Tocantins. Although the country has among the fewest cases in the region, it remains on high alert given the high transmissibility of the virus.
Highly contagious, measles spreads through the air through secretions from infected individuals and can infect people of all ages. Symptoms include high fever, a rash that spreads all over the body, nasal congestion, and eye irritation.
The disease can develop into serious complications, such as pneumonia, encephalitis, severe diarrhea, and even blindness, especially in malnourished children and people with compromised immune systems. Brazil had received the certificate of elimination of endemic measles in 2016 and, after facing reintroductions, regained that status in 2024.
For the head of the Laboratory of Respiratory Viruses, Exanthematous, Enteroviruses and Viral Emergencies at the Oswaldo Cruz Institute (IOC/Fiocruz), Marilda Siqueira, it is urgent to increase vaccination coverage.
"Measles is highly transmissible. We need to achieve at least 95% vaccination coverage to create collective protection in society, thus reducing the number of people susceptible to the virus," he warns.
In epidemiological terms, 'susceptible' individuals are those who lack protection against a given microorganism. In the case of measles, this is either because they have never been vaccinated, because they did not complete the two-dose regimen, or because they have not had prior contact with the virus.
When this group grows cumulatively over the years, a 'susceptible pocket' is formed, that is, a concentration of unprotected individuals that facilitates the circulation of the virus and increases the risk of outbreaks.
Until the early 1990s, measles was one of the main causes of infant mortality in the world, causing around 2,5 million deaths per year, mostly among children.
Vaccination coverage changed this scenario, allowing countries to progressively reduce cases and achieve the elimination of endemic circulation in several regions. In the Americas, this achievement was recognized in 2016, when the continent received the official certificate of elimination of the disease.
However, this achievement does not mean the virus has disappeared. The risk of reintroduction is constant, especially in contexts with low vaccination coverage. According to PAHO, most cases recorded in the Americas in 2025 occurred among unvaccinated people, while another significant portion involved individuals with unknown vaccination status.
Protection against measles depends on two doses of the vaccine. In Brazil, regular vaccination includes the first dose at 12 months and the second at 15 months of age, with other age groups potentially covered in specific campaigns.
"Children who do not have both doses registered in their vaccination records are not fully protected," confirms Marilda Siqueira, highlighting that adherence to the vaccination schedule is essential to prevent the return of measles.
According to PAHO, coverage in the Americas has not yet reached the 95% recommended to block the spread of the virus. By 2024, only 89% had received the first dose of the MMR vaccine, and only 79% had completed the second.
In Brazil, the situation is more favorable compared to the continental average. After years of decline, vaccination coverage began to grow again in 2023, with significant results in 2024. According to the Ministry of Health, the number of municipalities that reached the 95% target for immunization against measles, mumps, and rubella with the second dose of the MMR vaccine more than doubled in two years, rising from 855 in 2022 to 2.408 in 2024.
In 2025, faced with rising cases in neighboring countries, Brazil has been stepping up its immunization efforts, both in border areas and throughout the country. In the South, the reactivation of the Binational Health Commission with Uruguay resulted in a major joint mobilization in Sant'Ana do Livramento, Rio Grande do Sul, and Rivera, Uruguay, expanding protection for local residents and immigrants.
Furthermore, the Ministry of Health has promoted successive "D-Days" of measles vaccination in various states. In July, the campaign took place in border cities in Acre, Mato Grosso, Mato Grosso do Sul, and Rondônia, with approximately 3 doses administered. By August, all 79 municipalities in Mato Grosso do Sul participated in the campaign.
Marilda emphasizes, however, that no strategy will be effective if the population does not do its part.
"In conjunction with state and municipal departments, the Ministry of Health is working in municipalities with confirmed cases to prevent the spread of the virus. But this work will only be successful with the public's participation. This means seeking medical attention if you have a fever with a rash—those red spots on your body—and keeping your vaccinations up to date," he adds.
Measles is still seen by many as a 'childhood disease.' For researcher Marilda Siqueira, this perception was formed before mass vaccination, when the infection was more common among children and seemed less severe in wealthy countries, where there was better nutrition and access to healthcare. This interpretation, however, can be dangerous.
“The idea that it is a childhood disease is wrong: measles can affect any age group and cause serious complications, including death,” warns Marilda.
Recent PAHO data reinforce this assessment. In Mexico, most deaths recorded in 2025 occurred among Indigenous people aged 1 to 54, demonstrating that the disease is not limited to the youngest.
This means that, although children require special attention because they are more vulnerable, no age is free from risks. Vaccination at all ages remains the safest and most effective way to avoid complications and prevent the disease from returning.
In August 2025, the Pan American Health Organization (PAHO) issued an alert after noting a 34-fold increase in the number of measles cases compared to 2024. Ten countries in the Americas reported cases of the disease, totaling more than 10 confirmed cases and 18 deaths. Deaths were concentrated in Mexico (14), the United States (3), and Canada (1).
In Brazil, the most recent records indicate 24 cases by the end of August, 19 of them in Tocantins. Although the country has among the fewest cases in the region, it remains on high alert given the high transmissibility of the virus.
Highly contagious, measles spreads through the air through secretions from infected individuals and can infect people of all ages. Symptoms include high fever, a rash that spreads all over the body, nasal congestion, and eye irritation.
The disease can develop into serious complications, such as pneumonia, encephalitis, severe diarrhea, and even blindness, especially in malnourished children and people with compromised immune systems. Brazil had received the certificate of elimination of endemic measles in 2016 and, after facing reintroductions, regained that status in 2024.
For the head of the Laboratory of Respiratory Viruses, Exanthematous, Enteroviruses and Viral Emergencies at the Oswaldo Cruz Institute (IOC/Fiocruz), Marilda Siqueira, it is urgent to increase vaccination coverage.
"Measles is highly transmissible. We need to achieve at least 95% vaccination coverage to create collective protection in society, thus reducing the number of people susceptible to the virus," he warns.
In epidemiological terms, 'susceptible' individuals are those who lack protection against a given microorganism. In the case of measles, this is either because they have never been vaccinated, because they did not complete the two-dose regimen, or because they have not had prior contact with the virus.
When this group grows cumulatively over the years, a 'susceptible pocket' is formed, that is, a concentration of unprotected individuals that facilitates the circulation of the virus and increases the risk of outbreaks.
Until the early 1990s, measles was one of the main causes of infant mortality in the world, causing around 2,5 million deaths per year, mostly among children.
Vaccination coverage changed this scenario, allowing countries to progressively reduce cases and achieve the elimination of endemic circulation in several regions. In the Americas, this achievement was recognized in 2016, when the continent received the official certificate of elimination of the disease.
However, this achievement does not mean the virus has disappeared. The risk of reintroduction is constant, especially in contexts with low vaccination coverage. According to PAHO, most cases recorded in the Americas in 2025 occurred among unvaccinated people, while another significant portion involved individuals with unknown vaccination status.
Protection against measles depends on two doses of the vaccine. In Brazil, regular vaccination includes the first dose at 12 months and the second at 15 months of age, with other age groups potentially covered in specific campaigns.
"Children who do not have both doses registered in their vaccination records are not fully protected," confirms Marilda Siqueira, highlighting that adherence to the vaccination schedule is essential to prevent the return of measles.
According to PAHO, coverage in the Americas has not yet reached the 95% recommended to block the spread of the virus. By 2024, only 89% had received the first dose of the MMR vaccine, and only 79% had completed the second.
In Brazil, the situation is more favorable compared to the continental average. After years of decline, vaccination coverage began to grow again in 2023, with significant results in 2024. According to the Ministry of Health, the number of municipalities that reached the 95% target for immunization against measles, mumps, and rubella with the second dose of the MMR vaccine more than doubled in two years, rising from 855 in 2022 to 2.408 in 2024.
In 2025, faced with rising cases in neighboring countries, Brazil has been stepping up its immunization efforts, both in border areas and throughout the country. In the South, the reactivation of the Binational Health Commission with Uruguay resulted in a major joint mobilization in Sant'Ana do Livramento, Rio Grande do Sul, and Rivera, Uruguay, expanding protection for local residents and immigrants.
Furthermore, the Ministry of Health has promoted successive "D-Days" of measles vaccination in various states. In July, the campaign took place in border cities in Acre, Mato Grosso, Mato Grosso do Sul, and Rondônia, with approximately 3 doses administered. By August, all 79 municipalities in Mato Grosso do Sul participated in the campaign.
Marilda emphasizes, however, that no strategy will be effective if the population does not do its part.
"In conjunction with state and municipal departments, the Ministry of Health is working in municipalities with confirmed cases to prevent the spread of the virus. But this work will only be successful with the public's participation. This means seeking medical attention if you have a fever with a rash—those red spots on your body—and keeping your vaccinations up to date," he adds.
Measles is still seen by many as a 'childhood disease.' For researcher Marilda Siqueira, this perception was formed before mass vaccination, when the infection was more common among children and seemed less severe in wealthy countries, where there was better nutrition and access to healthcare. This interpretation, however, can be dangerous.
“The idea that it is a childhood disease is wrong: measles can affect any age group and cause serious complications, including death,” warns Marilda.
Recent PAHO data reinforce this assessment. In Mexico, most deaths recorded in 2025 occurred among Indigenous people aged 1 to 54, demonstrating that the disease is not limited to the youngest.
This means that, although children require special attention because they are more vulnerable, no age is free from risks. Vaccination at all ages remains the safest and most effective way to avoid complications and prevent the disease from returning.
The non-profit reproduction of the text is allowed as long as the source is cited (Comunicação / Instituto Oswaldo Cruz)
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