05/04/23
Hantavirus: a field study after the four cases of 2022
Last year, four people were hospitalized following infection with this rodent-borne virus. One had died. This high number and the more favorable clinical evolution – there had been seven hospitalizations including four deaths between 2008 and 2021 – led the ARS, Public Health France, the French Red Cross, the Pasteur Institute of Guyana (IPG ) and the Cayenne hospital center to carry out an active search for cases in the three districts concerned by the cases diagnosed in 2022, in Rémire-Montjoly and Macouria. No recent cases were detected, but fourteen old infections. The results were presented to residents last week.
In early 2022, four patients infected with hantavirus (Maripa virus, transmitted by an uncommon rodent in town) were admitted to the Cayenne Hospital Center. The situation was considered serious: in the previous fourteen years, only seven patients had been diagnosed; four had died (read the Professional Letter of May 3, 2022). It was to better understand the situation that several studies were carried out in the following months.
A telephone investigation and traps
It all starts with a telephone investigation carried out by the health monitoring and safety service of the Regional Health Agency (ARS). This investigation is done directly with the patient if possible or through a relative, then environmental surveys carried out by the ARS accompanied by the IPG (laboratory of Virus-Host Interactions) which place traps and capture rodents to search for hantavirus. This is systematically the case after the identification of a case of hantavirus. It is also an opportunity to propose solutions to avoid further contamination.
Results that challenge
The results call out: the people affected have hardly left their neighborhood while the most serious path of contamination passes through the Guyana pygmy mouse, a small brown variety known to live in open spaces such as savannahs or the edge of forests. The clinical course was also less unfavorable than expected: there was only one death among the four patients reported as infected last year, compared to 4 out of 7 during the previous period. The specialized teams then wondered whether other mild and therefore unreported cases had existed around the first four patients. It was therefore decided to actively search for traces of recent contamination in the surroundings of these cases, and to advance in the understanding of this disease and its circulation. The screening project was presented to the elected officials of the municipalities concerned.
A survey to understand
A serological survey around the last four cases therefore takes place from the end of November to mid-December. For two weeks in two sectors of Macouria, then a week in a district of Rémire-Montjoly, the teams of the French Red Cross carry out patrols in the three districts, explain the disease, offer a blood test to the inhabitants, ask them questions, give the results individually in the presence of the doctors of the CHC (UMIT), once they are known. Of the nine hundred people expected, two hundred and seventy-four participated. The analyses, carried out by the national reference center (CNR) hantavirus at the Institut Pasteur in Guyana, do not reveal any recent infection, that is to say during the last four months. On the other hand, 14 people show traces of an older infection. No significant difference was demonstrated between people carrying markers of an old infection (IgG) with hantavirus and the other people surveyed.
A major advance in the understanding of this disease
This is a major advance in the understanding of this disease: originally known to have a poor prognosis (nearly 50% of deaths), it now appears to be able to give symptoms weak enough not to require hospitalization. , biological sampling then reporting. The survey also shows that the virus did not circulate massively in the affected neighborhoods either.
A presentation of the results to the populations concerned
On Thursday and Friday, the results of the study were presented to the inhabitants of the neighborhoods concerned, who came in large numbers. It was explained that the study does not seem to indicate any particular circulation of hantavirus in these neighborhoods. Among these old cases, none has apparently required hospitalization.
A reminder of the recommendations
This restitution provided the opportunity for Adrien Ortelli, head of the environmental health unit at the ARS, and for the environmental health mobile team (Emse, successor to the Wash project) of the French Red Cross, to recall that rats are capable of transmitting other serious diseases, such as leptospirosis. And to remind you of a few precautions to take to avoid exposure to the virus: drive rodents out of your home, clean the dust with water and/or bleach (rather than with a broom, which can resuspend pathogens), and wear a mask, before cleaning a floor that has not been cleaned for a long time, to avoid inhaling the dust, do not hesitate to consult your doctor in the event of a high fever.
Last year, four people were hospitalized following an infection by this virus transmitted by rodents. One had died. This high number and the more favorable clinical evolution – there had been seven hospitalizations including four deaths between 2008 and 2021 – led the ARS, Public Health France, the French Red Cross, the Pasteur Institute of Guyana (IPG ) and the Cayenne hospital center to carry out an active search for cases in the three districts concerned by the cases diagnosed in 2022, in Rémire-Montjoly and Macouria. No recent cases were detected, but fourteen old infections. The results were presented to residents last week.
At the beginning of 2022, four patients infected with hantavirus (Maripa virus, transmitted by an uncommon rodent in town) were admitted to the Cayenne Hospital Center. The situation was considered serious: in the previous fourteen years, only seven patients had been diagnosed; four had died (read the Professional letter of May 3, 2022). It was to better understand the situation that several studies were carried out in the following months.
A telephone investigation and traps
It all starts with a telephone investigation conducted by the health monitoring and security service of the Regional Health Agency (ARS). This investigation is done directly with the patient if possible or through a relative, then environmental surveys carried out by the ARS accompanied by the IPG (laboratory of Virus-Host Interactions) which place traps and capture rodents to search for hantavirus. This is systematically the case after the identification of a case of hantavirus. It is also an opportunity to propose solutions to avoid other contaminations.
Results that challenge
The results are striking: the people affected have hardly left their neighborhoods while the most serious route of contamination passes through the Guyana pygmy mouse, a small brown variety known to live in open spaces such as savannahs or the forest edge. The clinical course was also less unfavorable than expected: only one death was reported among the four patients reported as infected last year, compared to 4 out of 7 during the previous period. The specialized teams then wondered whether other mild and therefore unreported cases had existed around the first four patients. It was therefore decided to actively search for traces of recent contamination in the surroundings of these cases, and to advance in the understanding of this disease and its circulation. The screening project was presented to the elected officials of the municipalities concerned.
A survey to understand
A serological survey of the last four cases is therefore taking place from the end of November to mid-December. For two weeks in two sectors of Macouria, then a week in a district of Rémire-Montjoly, the teams of the French Red Cross carry out patrols in the three districts, explain the disease, offer a blood test to the inhabitants, ask them questions, give the results individually in the presence of the doctors of the CHC (UMIT), once they are known. Of the nine hundred people expected, two hundred and seventy-four participated. The analyses, carried out by the hantavirus national reference center (CNR) at the Pasteur Institute in Guyana, do not reveal any recent infection, that is to say during the last four months. On the other hand, 14 people show traces of an older infection. No significant difference was demonstrated between people carrying markers of an old infection (IgG) with hantavirus and the other people surveyed.
A major advance in the understanding of this disease
This is a major advance in the understanding of this disease: originally reputed to have a poor prognosis (nearly 50% of deaths), it now appears to be able to give symptoms weak enough to do not require hospitalization, biological sampling and then reporting. The survey also shows that the virus did not circulate massively in the affected neighborhoods either.
A presentation of the results to the populations concerned
Thursday and Friday, the results of the study were presented to the inhabitants of the neighborhoods concerned, many of whom came. It was explained that the study does not seem pas indicate particular circulation of the hantavirus in these districts. Among these old cases, none has apparently required hospitalization.
A reminder of the recommendations
This restitution provided the opportunity for Adrien Ortelli, head of the environmental health unit at the ARS, and for the environmental health mobile team (Emse, successor to the Wash project) of the French Red Cross, to recall that rats are capable of transmitting other serious diseases, such as leptospirosis. And to remind you of a few precautions to take to avoid exposure to the virus: chasing rodents from your home, cleaning dust with water and/or bleach (rather than with a broom, which can suspension of pathogens), and wear a mask, before cleaning a floor that has not been cleaned for a long time, to avoid inhaling the dust, do not hesitate to consult your doctor in the event of a high fever.