A very contagious and difficult to treat disease has been detected in France. The Institut Pasteur is sounding the alarm.
A highly contagious disease is circulating in France. The Institut Pasteur warns against shigellosis which causes severe diarrhoea. A disease that is difficult to treat, in particular because the bacteria that cause it are becoming increasingly resistant to antibiotics.
• What is this disease?
Shigellosis, or bacillary dysentery, is an infection of the intestine caused by different bacteria of the Shigella type (Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei), also called shigella, explains Inserm.
In concrete terms, during contamination, shigellae invade the mucosa of the colon and cause an inflammatory reaction which leads to the destruction of the infected tissues. This causes severe diarrhea for the patient for three to four days.
This disease is extremely contagious: 10 to 100 bacilli are enough to cause infection. The disease kills around 200,000 people worldwide every year, including 65,000 children under the age of 5.
It is most prevalent in tropical regions where shigellosis is endemic all year round due to the lack of hygiene and sanitary infrastructure. But in recent years, foci have appeared in developed countries. In France, the National Reference Center for Escherichia coli, Shigella and Salmonella identified more than 1,300 strains of Shigella in 2019, detected eight epidemics of Shigella sonnei and one of Shigella flexneri, according to its annual report.
• What are the symptoms?
Shigellosis begins abruptly after a brief incubation. Among the symptoms: abdominal pain accompanied by vomiting; frequent, numerous or even haemorrhagic stools; but also fever and deterioration of the general state, details the Institut Pasteur on a page devoted to the disease.
Acute complications are particularly feared in infants and young children (hypoglycaemia, bacteraemia or sepsis, dehydration, collapse, acute renal failure, intestinal obstruction or peritonitis, Inserm list).
Chronic complications can also cause long-lasting malnutrition with severe growth retardation in height or weight.
• How is it transmitted?
The human being is the only reservoir of this bacterium. Since a patient can eliminate bacilli in his stool for weeks after a dysenteric episode, the risks of contagion are significant.
Concretely, shigellosis spreads by the fecal-oral route, in particular via water, contaminated food or even flies. In developing countries, the disease mainly affects children but also soldiers in operation, humanitarian personnel and tourists.
In industrialized countries, small outbreaks can occur in congregate settings for young children. But in recent years, two of these bacteria (Shigella sonnei and Shigella flexneri) have become epidemic within the male homosexual community. The Institut Pasteur even speaks of a “new sexually transmitted infection” and calls for more prevention.
“Analysis of the bacterial genome sequences and the characteristics of the cases, which occurred preferentially in adult males, suggest that these strains, originating in South Asia, are spreading in particular among men who have sex with men” , explains the Pasteur Institute.
• Why does it worry researchers?
Unlike gastroenteritis, “shigellosis cannot be treated by rehydration alone”, warns the Institut Pasteur. In principle, antibiotics allow rapid recovery without sequelae. But for several years, multi-resistant strains – particularly of Shigella sonnei and Shigella flexneri – have emerged. This considerably complicates the recovery of patients.
And the French population is not spared. A study published at the end of January in the journal Nature communications thus evokes against the “rapid” emergence in France of this “ultraresistant to drugs” disease. These highly antibiotic-resistant strains were indeed identified for the first time in France in 2015. They increased significantly until reaching a peak in 2021 with almost a fifth of cases.
These strains belong to the same lineage, Shigella sonnei, which became resistant to a key antibiotic some fifteen years ago in South Asia. The bacteria then developed this resistance to other antibiotics.
“It is entirely justified, given the knowledge of previous epidemics, to expect new epidemics of shigellosis in the coming years with these highly antibiotic-resistant strains”, warn the researchers.
For the most severe cases, the only effective antibiotics are carbapenems or colistin “which must be administered intravenously, which makes the treatment more aggressive with more complex follow-up in a hospital setting”.
• Is there a vaccine?
Several laboratories are working on the development of a vaccine. Clinical trials are underway and the first results seem encouraging. The Institut Pasteur has also developed a rapid diagnostic test by simple contact with a stool sample.
Scientists are also wondering about the different clinical forms of this infection and are wondering whether asymptomatic forms would not allow greater dissemination of the bacteria.
Its “high epidemic potential”, “the emergence of resistance to antibiotics” and “the morbidity linked to the long-term consequences due to recurrent infections” constitute, according to the Institut Pasteur, “a major public health problem”. The Shigella bacterium is also part of the WHO list of twelve priority pathogens for the search for new antibiotics.