Dengue Fever is the new viral bogeyman scaring the world. Don’t worry though, it is not a COVID 2.0, for various reasons: above all, because virologists and scientists say so, with absolute certainty. However, it is not a danger that can be underestimated either, since in some parts of the globe there have already been over a million cases of infection and, in the most serious cases, if not treated with the right drugs, this disease can even lead to death.
The first important difference with the SARS CoV-2 virus, whose memory is still fresh in all of us, is that it is a pathogen that has been known for centuries and for which there are already effective treatments and vaccines. We also know that it is a different viral family: not a Coronavirus, but a Flavivirus. The infection that affects humans is due to four different subgroups of this virus, called serotypes 1, 2, 3 and 4 (DENV-1,2 3 and 4). The second big difference with COVID-19 is that Dengue is not transmitted by air. ‘Human-to-human transmission is limited to very rare cases,’ reassures Professor Antonino Di Caro, Full Professor of Microbiology and Clinical Microbiology at Saint Camillus International Medical University of Rome – UniCamillus. ‘These are linked to blood transfusion and transplants or mother-to-child transmission during pregnancy, and have no real relevance in the development of epidemics.’ The large-scale spread of the infection, explains the Professor – who also received an honour from the President of the Republic for his service to the community during the recent pandemic -, is due to the action of certain mosquito species of the Aedes genus, commonly known as tiger mosquitoes. ‘These insects are capable of both transmitting the infection to humans and acquiring the infection from humans during the acute stages of the disease. A two-way transmission cycle is thus established between man and mosquito, which maintains and amplifies the epidemic‘.
The most common symptoms of Dengue are those common to other forms of influenza, with general malaise and prostration. They usually resolve within a few days. However, asymptomatic forms or, conversely, prolonged symptoms are possible. The most severe forms involve neurological involvement and even haemorrhage, but are mostly due to so-called re-infections (i.e. contracting the Dengue virus infection for the second time, but of a different serotype). ‘Dengue flu and COVID-19 have similar symptoms, but Dengue can progress to a severe form more rapidly‘, says pharmacologist Laura Scorzolini, UniCamillus Lecturer, Specialist in Infectious Diseases and collaborator of the research team of Professor Nicastri – Director of the Division of High Intensity Infectious Diseases at the Lazzaro Spallanzani Institute, and also UniCamillus Lecturer. ‘These more severe forms can occur in people who have pre-existing medical conditions, such as cardiovascular disease, diabetes or cancer; in the presence of co-infections, such as COVID-19 and Dengue at the same time; in pregnancy and in cases of immune system depression. These conditions can lead to life-threatening complications, such as bleeding, organ failure and shock. Severe symptoms include intense abdominal pain, persistent vomiting, breathing difficulties, bleeding gums‘.
Currently, virology experts agree that about half of the world’s population is at risk of contracting Dengue. Between 100 and 400 million infections are estimated each year. This disease – it is important to emphasise – poses a significant danger to people, but limited to the areas where it has become endemic, i.e. mainly urban and semi-urban areas in the tropical and subtropical belts of the planet. It is no coincidence that the worst scenarios at the moment are occurring in Central and South America and South East Asia. There, the situation is worrying and – as Professor Scorzolini further explains – ‘it is a real threat to public health that requires massive prevention and infection control measures to reduce the risk of the mosquito transmitting the infection to people as much as possible‘.
In any case, at the moment, the concern that a situation similar to what happened with COVID-19 will recur has no solid basis. While bearing in mind that nature is always capable of surprises, those who deal closely with this virus assure us that, like others of its kind, it has circulated for centuries and that, in the absence of transmission by the respiratory route, epidemics are generally more contained. Transmission via an animal vector means that the speed of transmission, and thus the risk of a pandemic, is not comparable with what happened in 2020. The mutation of the virus itself with this transmission system is also greatly slowed down compared with SARS CoV-2. In addition, scholars note an overall low inclination for our own mosquitoes to become vectors of this virus. There is therefore no evidence to suggest that a catastrophic scenario like the one that occurred in the recent past is likely to occur again.However, factors such as climate change, international travel, and connections between endemic and non-endemic areas cannot be ignored. These indeed, potentially allow the presence of Dengue cases almost anywhere. A case in point is the fact that it was recorded in the last six months of 2023 in Lombardy and Lazio, in people who had not travelled to tropical areas. This is why, emphasise Professor Scorzolini and Professor Nicastri, ‘It is important for anyone returning from an endemic country to make their doctor aware of the occurrence of flu-like symptoms in order to rule out Dengue virus infection. Rapid diagnostic tests, which can be carried out in most health facilities and emergency rooms, are available, and can ensure early diagnosis and appropriate treatment as well as greater control of infection transmission‘. Therefore, that is caution, no alarmism. ‘We have to worry just as much,’ Professor Di Caro concludes. And he aligns fully with the indications of his colleagues, ‘Italy has a great tradition of collaboration between human and veterinary health, and intervention plans have already been drawn up based on the surveillance of infections and the control of vectors. For my part, a recommendation also to the public and to my medical colleagues: since the diagnosis can also be performed at private facilities, all suspected or ascertained cases must be reported.Local vector control, to be carried out close to the places where the sick person has become infected, is of great importance in order to contain the spread of infection, and it is the responsibility of public health to do this‘.