Although it emerged just a few months ago, covid-19 has become the star disease of our days globally. Doctors around the world are striving to cure the greatest number of patients while, in parallel, numerous teams of scientists are working around the clock to develop a vaccine.
However, far from the spotlight, dozens of infectious diseases run their course . They are usually caused by viruses, bacteria, pathogens or fungi and, thanks to decades of research, in some cases we have vaccines that help protect us against them, but not in others. “All those that have effective vaccines and that are easily administrable are those that are closest to being eradicated”, points out the infectious disease doctor José Antonio Pérez Molina, spokesman for the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC).
The experts consulted agree that the disease that is closest to being eliminated is polio , which is only endemic in Afghanistan and Pakistan, where there is still an unvaccinated child population. So far, the only human disease that we have managed to eradicate has been smallpox, in 1980.
“If there is no vaccine, it is much more difficult, because it is the main prevention tool we have against infectious diseases”, highlights Pérez Molina. As the World Health Organization (WHO) recalls, the end of smallpox was achieved thanks to the collaboration of countries around the world. In the late 1960s, it was still endemic in Africa and Asia. Vaccination campaigns, surveillance and prevention measures undertaken to contain epidemic foci, together with better information for affected populations, were the strategies used to combat the disease.
“For vaccines to have their full impact on public health on global diseases, it is necessary to guarantee equitable distribution mechanisms and address any doubts that arise about vaccination”, highlights Denise Naniche, scientific director of the Barcelona Institute for Global Health (ISGlobal ), a center promoted by the “la Caixa” Foundation.
Below, we explain at what point are some infectious diseases that have gone into the background by the current pandemic of covid-19.
The SARS-CoV-2 coronavirus is not the only virus that has caused the global spread of a disease in recent times. HIV (human immunodeficiency virus) has been present throughout the world for decades, and, both due to its level of incidence and its transmission capacity, in this case we can also speak of a pandemic. According to data from UNAIDS, a UN agency specialized in the fight against this disease, in 2019 there were around 38 million people around the world with HIV. Since the first cases were detected in the early 1980s, some 35 million people have died from AIDS-related illnesses.
“HIV infection is already widespread in all countries and on all continents” , underlines Juan Carlos López Bernaldo de Quirós, president of the Spanish Interdisciplinary AIDS Society (Seisida) and doctor at the Gregorio Marañón University Hospital in Madrid. The expert recalls that, since the introduction of antiretroviral treatment for all infected people, the progression has been stopped and, in recent years, the number of patients has stabilized. “Despite this, in the Western world we have not yet been able to initiate a decrease in their number, and in Spain similar figures of new infections are maintained every year, between 3,500 and 4,000”, explains the researcher.
Another barrier is that there is still a percentage of patients without access to treatment, just over 30%. It is also worrying that part of the affected population does not know that they are: around 7 million people are unaware that they have HIV.
The development and improvement of antiretroviral treatments has been a turning point for those who have the virus. So much so that AIDS mortality has decreased by almost 40% since 2010. “Today we know that a person who takes treatment and has no detectable virus in his blood does not transmit the infection. The message that if a person with HIV is undetectable they cannot transmit the virus is important ”, emphasizes López Bernaldo de Quirós.
Thanks to antiretrovirals, the virus has been put at bay , but even so, it is not eliminated one hundred percent. And that is precisely the strategy that the researchers are following: what they are looking for is a total cure so that the infection does not reactivate if the treatment is stopped. As the scientist explains, multiple targets are being used to suppress this latent virus, such as drugs directed at the immune system so that it is able to recognize and eliminate viruses.
The vaccine to prevent or treat infection is another tool that is still in the running, but it is not an easy task due to the very nature of the disease. “The virus infects the CD4 lymphocyte, which is the cell of the immune system that is in the middle of the entire ‘immunological crossroads’, so the body cannot give an adequate response to the infection,” says the president of Seisida.
In addition, the fact that HIV mutates and changes the proteins that surround it makes the development of any vaccine difficult. Are we close to his disappearance? “I have no doubt that we will see the eradication of HIV, but, yes, it will take years,” says the researcher.
August 25, 2020 was a historic day for public health: the WHO certified that Africa was “free of wild polio” , after four years without detecting a single case. With this milestone, of the six WHO regions – the Americas, Africa, Southeast Asia, Europe, the Eastern Mediterranean and the Western Pacific – five are free of the polioviruses that cause poliomyelitis, so the elimination of the disease is closer. “Ending naturally-occurring polioviruses in Africa is one of the greatest public health achievements of our era and greatly encourages us to finish the work of eradicating polio globally,” said WHO Director-General Tedros Adhanom Ghebreyesus.
“The disease closest to eradication is polio,” confirms Ángel Hernández Merino, member of the Vaccine Advisory Committee of the Spanish Association of Pediatrics. Only two countries continue to register transmission of the virus: Pakistan and Afghanistan, both located in the eastern Mediterranean region. How has this historic achievement been achieved? Mainly, thanks to the massive extension of childhood vaccination campaigns.
In Pakistan and Afghanistan, some 50 million children had been left unvaccinated by the covid-19 pandemic , according to data from Unicef; Fortunately, in July the campaigns were resumed in both regions, the only places on the planet where poliomyelitis, a highly contagious disease caused by a virus that invades the nervous system and can cause paralysis in a matter of hours, is still endemic. Those under the age of five are the most vulnerable.
Following the success of smallpox eradication in 1980, eight years later WHO agreed to create the Global Polio Eradication Initiative, a public-private partnership led by national governments with various partners, including WHO, the Centers for Disease Control and Prevention, from the United States, Unicef or the Bill and Melinda Gates Foundation. Since the initiative was launched, the number of polio cases has decreased by more than 99%.
Measles is one of the diseases that can be prevented with a simple gesture: getting vaccinated. Even so, in 2017 it caused 110,000 deaths worldwide, and most of them occurred among children under the age of five, according to WHO data. The importance of vaccination is such that it is estimated that, between 2000 and 2017, inoculations prevented more than 21 million deaths worldwide, something that has been possible because the vaccine is included in the childhood vaccination schedule of the health systems of the countries.
However, its elimination does not seem close. “There is no date for its eradication because the goal looks distant. The situation is very different in different parts of the world, ”says Josefa Masa Calles, a specialist in Preventive Medicine and Public Health at the National Epidemiology Center (Carlos III Health Institute). In fact, in 2012, the WHO World Health Assembly approved the Global Vaccine Action Plan with the goal of eliminating measles in four WHO regions by 2015 and five by the end of 2020.
However, low vaccination coverage in some countries caused several regions – such as Romania, Italy or Greece in Europe – to suffer measles outbreaks in 2017, with the consequent increase in the number of deaths. In light of these data, the WHO expert group concluded that measles elimination “is seriously threatened” and that the disease has re-emerged in countries that had succeeded in eliminating it or were close to achieving it. As Masa admits, “if the goal is global eradication, the population in all areas of the world must be immune, and this is difficult to achieve, especially in a disease as contagious as measles.”
Its vaccine is included in the so-called triple viral, an inoculation that is usually done when the child is twelve months old and a second dose between three and four years old. This vaccine also protects against mumps and rubella.
As Angela Domínguez, member of the Working Group on Vaccinations of the Spanish Epidemiology Society explains, thanks to their effectiveness, the disease has been eliminated from thirty-five countries in Europe –among them, Spain– and from all nations. in the Americas region.
“But we cannot lose sight of the fact that elimination is a reversible situation, that in a country where measles has been eliminated, endemic transmission can be reestablished if transmission of the virus continues uninterrupted for twelve months or more,” the expert warns.
And we can’t forget about our regular winter visitor: the flu. Although it is very common, it is still serious. Every year, between 290,000 and 650,000 people die from respiratory illnesses related to seasonal flu, according to 2017 estimates. This reveals an increase from the previous global estimate, which placed annual deaths between 250,000 and 50,000. 500,000. It is an acute viral infection that spreads easily and circulates throughout the world. Most of those who suffer it recover in a week without medical attention, but there are also cases with complications; pneumonia and bronchitis are two flu-related respiratory illnesses that can lead to death. “The most serious forms that may require hospitalization, admission to intensive care units or death occur in people with risky conditions,” details Domínguez.
The best prevention method is vaccination, recommended for populations at risk such as health personnel, the elderly, pregnant women or chronic patients. Why do they have to get vaccinated every year? Due to the nature of the viruses that cause it, which change every winter, forcing experts to design new updated vaccines each season.
In this 2020, the covid-19 has forced the health authorities to advance the vaccination campaign to try to prevent the saturation of the health care system – as they are two infectious diseases with some similar symptoms. In addition, the Ministry of Health has made an extraordinary purchase of 5 million doses of vaccines to reinforce the campaign carried out by the autonomous communities and thus achieve greater vaccination coverage.
Although all diseases are concerned about their impact on health, some are more serious or have more cases than others. According to the Spanish Society of Tropical Medicine and International Health (SEMTSI), if we look at its incidence, Chikungunya fever or dengue – transmitted by infected mosquitoes -, the Zika virus disease – which had a major outbreak in 2015 stand out. in Latin American and Caribbean countries– or cholera –caused by a bacterium–.
But if we stop at its lethality, there would be Lassa fever –hemorrhagic viral disease–, Nipah virus infection –the virus host is a bat–, Ebola virus disease –which had an outbreak from 2014 to 2014. 2016 in West Africa and spread to other countries – or MERS – viral respiratory disease caused by a coronavirus.
“The most worrying infections are those that combine high transmissibility during an asymptomatic phase, high morbidity and mortality, and a high capacity for mutation and adaptation,” sums up Denise Naniche, scientific director of ISGlobal. In the case of diseases caused by the Ebola virus or by Nipah, their fatality rate – the number of deaths of the total infected – is higher than 50%.
