Nipah virus: age and respiratory problems increase risk of transmission
Nipah virus epidemics in Bangladesh: age and respiratory problems increase risk of transmission
Present throughout South and Southeast Asia, the Nipah virus is an emerging infectious agent transmitted by bats that, according to the WHO, poses a risk of a severe epidemic in the near future. While no treatment or vaccine currently exists, researchers at the Pasteur Institute, the CNRS and the Johns Hopkins Bloomberg School of Public Health have teamed up with international colleagues from the icddr, b (International Center for research against diarrheal diseases, Bangladesh), IEDCR (Institute of Epidemiology Disease Control and Research) and American CDC (control and prevention of diseases), to study the transmission dynamics of Nipah virus. They relied on data from epidemiological investigations carried out over the last fourteen years in Bangladesh, the most affected country. Their study showed that the risk of transmission is greater when the patient is an adult with respiratory symptoms. Therefore, when it is not possible to isolate all suspected cases, these individuals should be targeted as a priority to better fight against the spread of the virus. These results were published in the scientific journal NEJM today, May 9, 2019.
The Nipah virus is a bat-transmitted paramyxovirus that occurs in South and Southeast Asia. With a mortality rate above 70%, this virus is according to the World Health Organization (WHO) an emerging infectious agent likely to trigger severe epidemics if it evolves to gain transmissibility. This has led WHO to make it a research priority with the aim of preventing health crises.
In the absence of effective treatments or vaccines, the only way to control Nipah virus outbreaks is through targeted interventions that limit the risk of spread. However, setting up such interventions is difficult because the mechanisms of human-to-human transmission remain poorly understood.
To decipher the factors of the human-to-human transmission of the Nipah virus, researchers from the Institut Pasteur, CNRS, icddr, b, IEDCR, the American CDCs and the Johns Hopkins Bloomberg School of Public Health, have investigated the characteristics of all known cases of infection and more than 2,000 identified contacts during the last fourteen years of investigating the epidemics in Bangladesh, which reported the highest number of cases.
Their study showed that adult cases with respiratory symptoms infected more individuals than other cases. This result suggests that it may be useful to prioritize adults with respiratory problems when it is impossible to isolate all suspected cases.
In addition, contact subjects exposed to biological fluids, particularly respiratory secretions, have an increased risk of infection, which corroborates the major role of fluid secretions in the human-to-human transmission of the virus. The study also revealed that spouses of infected persons and long-term contact subjects had a higher risk of infection. As a result, these individuals must be subject to enhanced protection measures.
"Only a thorough understanding of the Nipah virus transmission factors can effectively stem the transmission of the virus during an outbreak. In this regard, the extensive investigations carried out in the last decade by our colleagues from icddr, b and IEDCR in Bangladesh, have made it possible to answer key questions about the human-to-human transmission of the virus, "says Simon Cauchemez, co - Principal author of the study and head of the Mathematical Modeling of Infectious Diseases Unit at the Institut Pasteur.
The risk of transmission of the Nipah virus depends on the characteristics of the patient, such as age and the presence of respiratory symptoms. As Birgit Nikolay, first author of the study, explains: "The results of this study help to identify which patients should be targeted with isolation measures if it is not possible to isolate all patients. suspected cases. This prioritization could help to better control the spread of the virus during major outbreaks. "
Despite these findings, gaps remain in understanding the transmission of the Nipah virus. Future research will focus on studying how the virus spreads in the human body, and on improving the criteria for identifying super-transmitters. Further studies are also planned to better understand the dynamics of virus transmission in bats, thus predicting where and when transmission between the animal and humans is most likely to occur.
