The United States, which declared itself measles-free in 2000, has seen a recent spike in measles infections. Since the beginning of this year, measles infections have been detected in many states in the United States. The latest data from the Outbreak Response Innovation Center at Johns Hopkins University in the United States show that 1284 confirmed cases of measles have been reported in 2025, that compares with an average of about 180 cases a year in the United States.
Measles is an acute respiratory infectious disease caused by the measles virus. Since measles was eliminated in the United States 25 years ago, why the resurgence? Measles is highly contagious. How can the public prevent it? July 10, science and technology daily interviewed Li Dongzeng, chief physician in the Department of respiratory and Infectious Diseases at Beijing You’an Hospital, and Bai Yunhua, chief physician in the Department of Planned Immunology at the Beijing Chaoyang District Center for Disease Control and Prevention.
Official declaration of“Elimination”, why will the outbreak again?
“If the incidence of a disease is controlled to a very low level, we usually think of the disease as ‘eliminated, ‘” Bai explained, but elimination is not elimination. Some developed countries have reached the“Elimination” stage of measles, when there are still very low levels of measles virus infection and transmission, and infections can occur if immune barriers are not strengthened.
This“Resurgence” is also related to the characteristics of the measles virus. The measles virus is highly transmissible from person to person in the absence of an immune barrier, and is currently considered to have an Basic reproduction number (R 0) of 18, meaning that an average of 18 susceptible individuals can be infected per measles patient.
Li Dong once told a reporter that measles is very contagious. People who don’t have immunity to measles have a 90 percent chance of being infected if they come into contact with someone who has measles. In addition, measles infection will appear basically fever, rash and other symptoms, recessive infection, asymptomatic infection is rare.
So“Eliminating” measles doesn’t mean it won’t happen again. Once the immune barrier“Loose”, the measles virus will take advantage. “The infectious nature of the measles virus means that as soon as vaccination rates drop, the incidence of measles starts to rise,” Li Dong said.
Vaccine hesitancy or the biggest obstacle?
Why is the immune barrier“Loose”? Is it because the vaccine isn’t protective enough?
“Worldwide, measles-related deaths have fallen by about 79% , and the number of people involved could reach 171 million, thanks to mass measles vaccination,” said Bai, at present, the actual protective effect of measles vaccine after vaccination has fully demonstrated its safety and effectiveness.
“The measles vaccine is very effective. In our country, the measles-mumps-rubella-mumps (MMR) vaccine is included in planned immunization, and children with normal immunity are almost free of measles after two doses of the vaccine,” Li Dong said.
The effectiveness and safety of measles vaccine has been verified by large-scale population, but why is it difficult to form a population-wide immune barrier?
“Globally, the biggest problem in measles prevention and control in the last two years has been a trend of ‘vaccine hesitancy, ‘” Li Dong said, citing anti-vaccine movements and vaccine rumors in some European and American countries, as a result, many people have doubts about the safety, efficacy, and necessity of the vaccine, resulting in a decline in measles vaccination rates in these areas.
Bai yunhua said that because of“Vaccine hesitation”, some developed countries have seen an abnormal decline in vaccination rates in recent years, which has led to the“Resurgence” of infectious diseases that had been well controlled. The situation is likely to worsen if proper immunization programmes are not resumed as soon as possible.
What should be done when deaths occur?
“Severe measles can lead to complications such as laryngitis, pneumonia, myocarditis and encephalitis, which can be fatal,” Li Dong warned, the younger the age, the higher the risk of weight loss. In addition, people with immunodeficiency, low immunity and basic diseases are prone to develop severe disease after infection.
“Don’t blindly think that you are not suitable for vaccination or contraindicated people, you can consult a professional doctor if in doubt,” Li Dong has stressed that vaccination can effectively prevent infection and avoid weight gain.
In order to scientifically and accurately carry out the work of measles prevention and control and diagnosis and treatment, the national health department and the National Disease Control Department timely issued relevant prevention and control and diagnosis and treatment plans, and strengthened monitoring, analysis, research and judgment, timely detection, standardized treatment and effective treatment will keep the incidence of measles at a low level.
Bai Yunhua, in addition to routine immunization, our country carried out several rounds of measles supplementary immunization activities, further narrowing the immunization gap. With the implementation of various measures, the annual reported incidence of measles in our country has continued to decline, and has reached the lowest point in history in recent years.
“The prevention and control strategy for any infectious disease is a combination of comprehensive measures,” Bai said, adding that the public should complete vaccinations in time, especially before pregnancy, women of childbearing age, infants and young children of the right age should be timely vaccination procedures and professional recommendations to avoid severe and complications.
“In order to cope with the import pressure in measles endemic areas around the world, we still need to maintain high vaccination rates, continue to maintain the high-quality operation of the measles surveillance and reporting system, deal with outbreaks in a timely manner, maintain surveillance sensitivity at ultra-low incidence rates and high vaccination rates for immunization programmes, and continuously reduce the prevalence of infectious diseases,” said Bai.