Spread the love

With the fiery summer, the four-year World Cup will begin in Russia. Recalling the summer of four years ago, in addition to the enthusiasm of the “Samba style” sweeping the world, lingering in the minds of many people, as well as the terrible mysterious virus that ravaged the West African continent – Ebola. Like SARS, when people faced Ebola in the past, they were almost completely helpless except for the symptomatic treatment of infected patients and strict guarantees for the isolation of those who were not infected. Nearly a year after that, Ebola only “grew away”. After it disappeared, where did it go, when did it appear in front of mankind in what form, and people did not know about it. In short, this battle ended in human defeat.

In the past four years, human beings have devoted considerable resources to conducting related research in order to respond effectively to the next Ebola outbreak. A number of specific “spleen” aspects of the Ebola virus have been revealed, and vaccines that can effectively target it have also been developed. We have reason to believe that the next time we “fight”, the human response must be more calm and effective. However, the virus always reminds human beings in various ways, and should always be cautious and humble before the natural.

Figure 1. A street in a village in Sierra Leone. A few minutes before the photo was taken, a woman died of Ebola infection in a room at the end of the corridor. She became infected after attending the funeral of Ebola’s death in another town. Unfortunately, after her death, dozens of people in the village died of illness due to her infection. (Source: U.S. Centers for Disease Control and Prevention)

At the beginning of this year’s summer, the Nipah virus disease (NVD) was reported in Kerala, southwestern India. As of May 28, 14 people have already died of NVD. At the same time, more than 30 people are seriously ill and hundreds of people have been isolated. What is this Nipah virus? Why do many people say it is the next Ebola?

Unveil the virus

The Nipah virus really entered human vision at the end of the last century. A new virus that seriously harmed domestic pigs and humans was first discovered in Malaysia in 1998. It was originally thought to be caused by the Japanese encephalitis virus because of its symptoms of encephalitis. In February 1998, Nipah virus was first isolated from the serum of patients with NVD, and this virus was isolated from the diseased horse in the diseased horse in the Hendra area in the suburbs of Librichban, Queensland, in 1994. The genotypes are 21% different and the amino acid sequence is 11% different, so it was originally named “Hendra-like virus”.

In March 1999, as further identified by the US Centers for Disease Control, the virus was a new virus. Since the virus was first isolated from a patient in Nipah Town, Malaysia, the virus was named Nipah, and Ebola virus is an RNA negative-strand virus and belongs to Paramyxoviridae. Other viruses in the same family include measles virus, mumps virus, human respiratory syncytial virus, etc. Nipah virus and Hendra virus belong together. The family is a member of the genus Fox.

From October 1998 to May 1999, NVD had a large-scale outbreak in Malaysian pig populations and populations. As a result, 265 pig workers became ill, 105 died, and 116 million pigs were killed. The disease then spread to Singapore. . NVD was first reported in Bangladesh in 2001, and an outbreak occurs every year in the country. Diseases are also reported occasionally in eastern India, with case fatalities varying from 75% to 100%.

Figure 2. An unknown virus that caused dozens of deaths was reported in the Philippines in 2005. After WHO sent a team to assist in the investigation, it was confirmed that the culprit was Nipah virus. The picture shows investigators taking home pig blood samples for analysis. (Source: U.S. Center for Disease Control and Prevention)

According to statistics, from 1998 to 2015, there were more than 600 cases of Nipah virus infection reported worldwide. Due to its high morbidity and high mortality rate, the U.S. Centers for Disease Control and Prevention listed it as the most dangerous biosafety level 4 virus.

Figure 3. Schematic map of the outbreak of the Nipah virus outbreak (blue squares) and fruit bats (Source: U.S. Centers for Disease Control and Prevention)

Current research shows that endothelial cells (such as vascular endothelial cells) and nerve cells in the body are the main targets of Nipah virus. The F and G proteins of the virus can mediate the formation of cell syncytia and enter cells to cause infection. Nipah virus-mediated cell syncytia can be formed on a variety of animal-derived cell lines, which may be the theoretical basis for the widespread infection of many mammals by Nipah virus.

Ebola’s natural host is still not clear, unlike the fact that the Nipah virus carrying and infected in nature is considered to be the fruit bat of the genus Pteropus. Due to the specificity of the bat’s own immune system and heredity, many The virus can infect bats without causing the disease, and its wide range of distribution and flight range also makes the virus spread more widely. Pigs are considered to be potential “amplifier” hosts for Nipah virus. The virus can be replicated in large numbers in infected pigs and transmitted to normal herds or people through saliva or other body fluids. This is also one of the terrible aspects of the Nipah virus. Their distance from humans is not really far away. In the epidemic reported in the past, the case of a nurse or family member who had been nursing an infected person in Bangladesh and eventually infected with Nipah virus also confirmed that Nipah virus can be transmitted from person to person.

Figure 4. Training Photographs of Biosafety Level 4 Laboratory Staff Provided by the U.S. Food and Drug Administration (Source: The U.S. Food and Drug Administration on Visual hunt)

Virus intrusion

Due to the neurophilic nature of the virus, the infected person mainly presents with neurological symptoms and respiratory symptoms. The incubation period for swine infection is approximately 7 to 14 days. The clinical symptoms of pigs of different ages are different. The typical symptoms of the respiratory tract are usually acute fever, dyspnea, mild or severe cough, and severe respiratory sound. Severe cases show diseased pigs coughing blood; sick pigs usually also have neurological symptoms such as tremors, muscle spasms and convulsions, which may be confused with the symptoms of JE infection, and the high incidence and low mortality in pigs, these factors make it safe Increased risk.

After a person is infected, the incubation period is about 1 to 3 weeks. The severity of clinical symptoms is different in different patients. Symptoms of infection with Nipah virus include varying degrees of headaches and fever. Some patients experience lethargy, confusion, cramps, and tremors. They develop into coma after a few days, and even die in drowsiness. Patients who experience coma may appear permanent. Brain damage. It has also been reported that some cases died only months or even years after the latent infection with Nipah virus. Due to the eosinophilic nature of the virus, infection can cause extensive vascular inflammation, and damage to the cerebral cortex and subcutaneous endothelial cells. The virus in the cerebrospinal fluid replicates in large numbers, resulting in extremely high NVD mortality.

Figure 5. Fruit bats that carry the Nipah virus in nature (Source: https://visualhunt.com)

Prevention and control of Nipah virus

Perhaps due to the geographical constraints of the outbreaks, human enthusiasm and interest in the Nipah virus appear to be limited. A depressing status quo is that the current treatment for Nipah virus is limited to supportive care for acute symptoms, and no specific drugs or vaccines have yet emerged. This is also one of the reasons why WHO and related professionals are worried about the potential epidemic.

Since Nipah virus encephalitis can be transmitted from person to person, standard infection control measures and self-protection of the TCM staff during the nursing process are very important. Laboratory studies have shown that ribavirin is effective against viruses in vitro, but human studies have so far been inconclusive, and the clinical use of ribavirin is still uncertain; already evaluated in the ferret model Viral use of human monoclonal antibodies targeting the viral G glycoprotein was found to be effective.

Regarding prevention, only a subunit vaccine against Nipah virus G protein in Australia was used to prevent horse infection with Hendra virus and other human or veterinary vaccines used in laboratory research. But all in all, none of the preclinical studies for the Nipah virus treatment or prevention vaccines can be done. People may only be able to prevent Nipa by avoiding contact with sick pigs and bats in endemic areas and not drinking fruit and vegetable juices. Viral infection.

Figure 6. There is currently no effective vaccine or drug for Nipah virus (photo source: https://visualhunt.com)

Nipah virus in China?

For China, although there is no case of Nipah virus infection yet, as early as in 2009, the researchers of the new infectious disease research group of the Wuhan Institute of Virology, Chinese Academy of Sciences, first detected the origin and evolution of SARS in bat research, and in our country The presence of antibodies to Nipah virus or nipavirus in bats in Yunnan suggests that there may be a natural source of Nipah virus or similar virus in our country.

With the development of logistics convenience and trade globalization, the inflow of foreign viruses is a huge hidden danger for China’s economic security and people’s health. At the same time, China is a big country for feeding and eating pigs. It is conceivable that pigs and people without protective antibodies will have little resistance once the outbreak occurs. Therefore, it is of great significance to carry out reserve research work in advance, establish test standards and develop effective vaccines for China to avoid major economic losses and prevent and control the occurrence of major epidemics.

Although there is no direct scientific relevance, some of the epidemiological characteristics of the Nipah virus make it possible for the author to think of another zoonosis, the flu virus. For human society, the flu virus does not know how many generations have evolved with humans and has evolved into a type of public health problem that has such a major impact on human health and the economy today.

For the process of mankind conquering nature and transforming nature, it may have always been a process in which human beings explore the natural process step by step. They always test the bottom line of nature with impunity, thinking that they can completely conquer nature. However, nature will always warn arrogant humans in some form. There is a huge limitation to what we already have. In the process of exploring nature, what humanity needs is not only high-tech means but also a sense of respect for nature.

Figure 7. Liberia villages and towns that have been outbreaks of the severe Ebola outbreak can be easily spread on a large scale in such squatter settlements where the density of inhabitants is extremely high.

Leave a Reply

Your email address will not be published. Required fields are marked *