It’s a mystery that has occupied the minds of doctors at the Children’s Hospital of Eastern Ontario in Ottawa this summer. The story begins with the arrival in the emergency room of a 9-year-old boy, a week after a camping trip in northern Ontario. The child, who appears to be in good health, feels very ill during his hospitalization. He presents several worrying symptoms: fever, stiff neck, headaches, etc. The medical team first thinks it’s bacterial meningitis and administers antibiotics. To no avail. Indeed, the little patient’s condition quickly deteriorates: his consciousness is severely impaired, he has difficulty speaking, and barely reacts when someone speaks to him. He still presents with a stiff neck, muscle weakness, etc.
Everything points to severe viral encephalitis, i.e. inflammation of the brain. However, doctors, who carry out multiple tests, do not find the slightest trace of the usual suspects: enterovirus,herpes simplex (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV), human herpes virus type 6 (HHV-6), parechovirus, Epstein-Barr virus. While the child was placed in intensive care, the trail pointed towards autoimmune encephalitis: basically, the immune system would attack the brain. This time, the little patient received treatment aimed at calming this immune runaway. And, finally, his condition improved. After about two weeks, he was finally able to leave the hospital and, after several weeks of convalescence, returned to normal neurological condition.
ALSO READ Crimean-Congo Hemorrhagic Fever Virus Discovered in Corsica, and It’s Just the BeginningBut the case does not end there. Because it was not autoimmune encephalitis that nearly killed the child. Two months after leaving the hospital, doctors received the serological tests, which revealed an infection with the Powassan virus, a rare pathogen responsible for severe encephalitis, with a high mortality rate of around 10 to 15%. Around 50% of survivors of a serious infection suffer from long-term neurological after-effects: chronic headaches, cognitive and memory disorders, motor disorders, difficulty speaking, etc. This virus is transmitted within fifteen minutes of the bite of a tick of the Ixodes genus (Ixodes scapularis, Ixodes cookei et Ixodes marxi), during his blood meal. However, the child, who had just returned from a camping trip, showed no visible signs that could have put doctors on the right track earlier.
Crimean-Congo haemorrhagic fever virus discovered in the Pyrénées-Orientales and Corsica
So the story ends well, but it is indicative of an increasingly worrying change in the field of infectious diseases. With global warming, some species of ticks can live and reproduce in areas where they were not previously present or were, at least, not very active. With winters also being less harsh, they have a better survival rate and their populations are increasing. Earlier springs and later autumns extend their periods of activity and therefore of bites.
All this contributes to increasing the risk of infections. A recent example of this phenomenon is the Crimean-Congo haemorrhagic fever virus, similar to Ebola, which was discovered in recent months in the Pyrénées-Orientales and Corsica. It is transmitted by ticks. Hyalomma marginatumwhich are gradually settling in the south of France due to climate change. While Crimean-Congo, Powassan and many others are still rare, or even absent, in Europe and North America, they should become more familiar in the coming years with the announced invasion of these fearsome blood-sucking ticks.
