The Texas State department of Health (USA) has reported the first measles death of an unvaccinated school-aged child. Since the end of January, 124 cases of the disease have been confirmed, mostly in children.

The Texas outbreak is an example of what has been happening globally for the past few years: the issue of measles cases is growing. In 2023 alone, there were an estimated 10.3 million worldwide, an increase of 20 % compared to 2022. It is estimated that more than 100,000 people died from the disease in 2023, most of them children under 5 years of age.

Europe also shows an increase, with Romania being the most affected country, with more than 80% of the diagnoses. In Spain, despite being in official measles elimination status since 2016, an increase in cases and outbreaks has been statement since 2023. In addition, transmission of the disease has been identified in the healthcare setting.

 

Measles is caused by a virus of the genus Morbillivirusfamily Paramyxoviridaewhich is found worldwide. Along with rubella, roseola, fifth disease, fifth disease erythema infectiosum and chickenpox, it is one of the five classic childhood rashes, i.e. the typical childhood illnesses with rashes or pimples on the skin and fever.

Humans are the only host of this virus, which is not very variable, so the immunity it causes lasts a lifetime and is generally passed only once.

The measles pathogen is one of the most transmissible pathogens available. For example, it is 10 times more contagious than SARS-CoV-2, for several reasons:

• The infective dose is very leave, in other words, you do not have to be exposed to a large amount of virus to become infected.

• Conversely, the amount of virus expelled by an infected person is very high. The combination of these two factors are the best for the virus... and the worst for us.

• It is spread through the air. A person with measles spreads the virus by breathing, coughing or talking, and the virus can remain airborne for a period of time. It has been estimated that a child who enters a room (a day care center, for example) two hours after another child with measles has been in the room could become infected.

• A person with measles can be contagious for about eight days, even before the disease manifests itself. Before we even know we have it, we are already spreading it to others without anyone noticing. In addition, because vaccines have reduced the number of cases so much, younger healthcare staff are not used to recognizing it and diagnosis can be delayed, which means that the sick person can continue to spread the virus.

The first sign is usually a high fever, which begins about 10 to 12 days after exhibition to the virus and lasts 4 to 7 days.

In the initial phase, the patient may present with mucus, cough, watery and red eyes, and small white spots on the inside of the cheeks. After several days a rash appears, usually on the face and upper neck, which spreads and eventually affects the hands and feet. It lasts 5 to 6 days and then fades away.

Most deaths are due to complications of measles, which are most common in children under 5 and adults over 30. The most serious complications are blindness, encephalitis, severe diarrhea - which can lead to dehydration - ear infections and severe respiratory infections such as pneumonia.

Severe cases are particularly frequent in young children who are malnourished or whose immune system is weakened by other diseases, in which case the death toll can be as high as 30%. The infection can also cause serious complications in pregnant women, including miscarriage or premature delivery. However, those who recover become immune for life.

On the other hand, infection causes a loss of immune system report cells, resulting in a kind of immune amnesia against other pathogens. This "cleansing" of the immune report is the manager of the increased susceptibility to opportunistic pathogens. It can last from a few weeks to months, and is the reason that measles mortality is typically caused by secondary infections due to other respiratory or digestive tract pathogens.

There is no specific treatment and the only preventive measure is the vaccine, which contains attenuated strains of the virus and is administered in combination with the mumps and rubella vaccine: the measles/mumps/rubella MMR.

It is administered in two doses in the common childhood vaccination schedule: at 12 months of age and at 3-4 years of age. The efficacy to prevent the disease is 93 % with one dose, reaching almost 100 % when the second dose is administered. It confers lifelong protection.

It is estimated that between 2000 and 2015, the vaccine prevented more than 20 million deaths worldwide, making it one of the best investments in public health. In order to control and eradicate the disease, it is essential that vaccination coverage is at least 95%, that is, that 95% of the population has been immunized with the two doses. The global goal is to eliminate the disease by 2030.

If we have a good vaccine that is effective, safe and free, why are measles cases increasing worldwide, is it the fault of antivaccinationists, are they all imported cases, has the vaccine stopped working? There is probably no single cause and the answer will depend on the context.

Indeed, it can sometimes be due to a vaccine refusal attitude. We do not know why the school-age child who died of measles in Texas was unvaccinated. Most cases in children are due to non-vaccination, and refusal of immunizations increases measles.

Perhaps he suffered from some other immunosuppressive disease and vaccination was not recommended at the time, or perhaps his parents were anti-vaccine. In any case, measles immunization is an excellent example of what is known as the herd effect: being surrounded by vaccinated people is the best way to prevent the disease in vulnerable people who cannot be vaccinated.

As the vaccine is almost infallible after the second dose, cases of measles in vaccinated children under 3-4 years of age may be due to the fact that they have not reached maximum protection: either they are under 12 months of age and have not yet been vaccinated or they have not yet received the second dose.

As far as adults are concerned, there is one age group that is more susceptible to measles: those born between 1971 and 1981, since in the 1970s a single-dose vaccine was used that did not fully protect against measles. Two-dose vaccination began systematically in Spain in 1981. It is assumed, therefore, that those born after that year would be correctly immunized, unless they are missing the second dose.

And what about the older ones, those born before 1970? Probably, most of them had measles as children. At that time there was no vaccination, the virus circulated freely and, as we have said, this disease is very transmissible and having passed it immunizes. Therefore, cases in people over 55 years of age are very rare.

Finally, another factor influencing the increase in the disease is imported cases. Romania and Morocco, with lower vaccination coverage, now have active epidemics and there is a significant influx of people. As the virus is so contagious, these people can easily generate secondary cases if they reach susceptible individuals: children under 3-4 years of age without the two doses and unvaccinated people or without natural immunity.

The places where transmissibility and vulnerability are higher (closed places, nurseries with small children, health centers where sick people go) are where outbreaks can be more easily registered. This would explain the increase of infections in healthcare staff (adults between 45-55 years of age) in Spain during the last year.

The risk of infection in the general population in Spain is considered low due to the high vaccination coverage in Spain (97.2% with one dose and 93.9% with two doses). However, as long as the high incidence status continues in some countries in our environment, it is expected that cases and outbreaks will continue to appear in the population without immunity to the disease.

Vaccination and early identification of suspected cases, with special attention to the 1971-1981 age group or susceptible population, are essential to achieve the goal of eradicating measles, and this will be achieved through vaccination.