Five years ago to the day, Beijing announced its first death from atypical pneumonia, subsequently named “Covid-19”. Today, the WHO counts 7,079,129 deaths linked to the pandemic across the world. But in 2025, other viruses must be monitored because they emerge or develop enough to, perhaps, raise fears of a possible return to this dismal period in the future.
Mpox, formerly called “monkey pox”
Isolated for the first time in 1958 in a monkey colony in Copenhagen, hence its initial name “monkey pox”, it is in fact rodents which transmit it to humans. Between men, the mpox virus is transmitted by physical contact, contact with contaminated materials and respiratory droplets. Then, symptoms develop during the incubation period between three to twenty-one days, and last two to four weeks. Distressing and painful, symptoms include rash with blisters progressing to crusts, fever, headache, muscle pain, swollen lymph nodes and fatigue. While most people recover without treatment, the illness can be serious or even fatal.
With 28,682 cases and nine deaths recorded in 2024, Europe is the main focus of the disease, followed by Africa with 15,267 cases and 77 deaths in 2024, including 9,513 cases in Congo in mid-December. In the continent, the increase is worrying because it is constant every month. As of January 7, 2025, the 5,250th case was declared in France out of 117,663 cases worldwide.
The modified version of avian flu, or modified H5N1
Researchers around the world are on alert. The H5N1 avian flu virus, already formidable in its natural form, is the subject of controversial laboratory experiments. Scientific teams have successfully genetically modified this virus, raising concerns about potential risks to global health. Because if it was not transmitted to humans before, these modifications made to H5N1, manipulations originally aimed at anticipating natural mutations and developing countermeasures, give it alarming capabilities: more efficient replication in mammals and increased resistance to the immune system. And the symptoms are similar to Covid-19. Modified H5N1 has a potential mortality rate similar to natural H5N1, approximately 58% of those infected.
The World Health Organization (WHO) is closely monitoring the situation as the recent appearance of cases in other species, notably cows in Texas, is rekindling fears. The main risk would be that the virus spreads among pigs, an ideal interspecies bridge because they have the same sialic acid receptors as humans in their respiratory tract.
The flu virus
A pathogen once again that affects the respiratory tract, the influenza virus exists in four forms A, B, C and D, of which types A and B are the most to fear. A viral disease feared every winter, the flu manifests itself by a set of characteristic symptoms which often strike suddenly. The flu virus can turn into a pandemic for several reasons, notably because there is not just one flu, but flus.
First, the genetic variability of type A, in particular, evolves rapidly through frequent mutations. This ability allows it to escape the immunity acquired by people who have already fallen ill. Its genetic reassortment makes it very dangerous because when a host is infected with two different influenza viruses simultaneously, a shuffling of genes can occur, creating a new, potentially more dangerous virus. It is transmitted between species, animals and humans, which increases the risk of emergence of new strains and rapid diffusion.
-All of these factors combined explain why the influenza virus, particularly type A, has the potential to cause a pandemic, similar to the Spanish flu of 1918 (type H1N1) which caused between twenty and fifty million deaths. For the moment, each year seasonal flu is responsible for 290,000 to 650,000 deaths worldwide according to the WHO, out of a billion recorded cases.
SARS-CoV-type coronaviruses
Having become famous since 2019, coronaviruses are now generally associated with benign illnesses such as colds or mild flu-like illnesses. However, some strains have evolved, becoming more aggressive and highly contagious. SARS-CoV is a perfect example: this virus can cause severe acute respiratory syndrome (SARS), which is potentially fatal. Between November 2002 and July 2003, a SARS epidemic affected thirty countries, causing 774 deaths according to Inserm. Responsible for the 2019 pandemic, SARS-CoV-2 is a close, yet distinct, form of it.
Moreover, in the face of these emerging threats, the World Health Organization has included all coronaviruses on its monitoring list of emerging viruses. This decision highlights the importance of vigilance and continued research in this area.
The respiratory virus HPMV or MPHV
The HMPV virus (Human Metapneumovirus) is a respiratory pathogen discovered in 2001 in the Netherlands. Contagious, it mainly affects children under 5 years old and is spread by respiratory droplets and direct contact with an incubation period of three to six days. The deceptive HPMV virus presents symptoms similar to those of the flu: fever, cough, wheezing and nasal congestion, but nevertheless causes infections of the upper and lower respiratory tract. Very dangerous for infants, the elderly and immunocompromised people, it is the second most common cause of acute respiratory infections in young children and can lead to pneumonia or bronchiolitis.
In northern China, cases of human metapneumonivirus are exploding but nothing alarming for the moment. The risk of a pandemic is low although cases of contamination have also been reported in India.
Today, the WHO estimates that the number of emerging viruses is likely to increase because modern lifestyles favor them through: environmental changes, notably deforestation, since contact between humans and animals is more present, changes climate and human activity which modify the geographical distribution of species, introducing new disease vectors, the increase in global population density, especially in urban areas of low-income countries, increases the risks of transmission, and via improving transportation and increasing flows of people, accelerating the global spread of pathogens.
