The West Nile is back. West Nile fever

This summer, Mrs. Catherine de Ville of Texas, USA "lost" her life for a month-after being bitten by mosquitoes, she lay in the hospital for eight days, had to spend her birthday in a hospital bed, and missed her daughter's first day of school. After leaving the hospital, she had a rest for a while.

On July 30, De Ville felt that he had the flu, accompanied by symptoms such as high fever, chills and rash. She doesn't know under what circumstances she was infected. "Maybe she is swimming, maybe she is cooking." On August 8, De Ville's condition deteriorated with a severe headache. "It's like an axe cut off my head," she described. "I am in pain. I already have a migraine, which is even worse. " The next day, De Ville went to the emergency room of the Methodist Dallas Medical Center and was told that he was infected with West Nile virus.

"Strangely, I'm a little relieved." She cried and said, "On the one hand, at least the disease has an exact name. On the other hand, I know that I will not infect other family members, which is very important to me. "

According to statistics, about 80% of people infected with West Nile virus are invisible and have no symptoms, only virus carriers; About 20% of infected people will have "West Nile fever". Unfortunately, de Ville is in this 20%; Fortunately, she didn't die of it. According to the data of the US Centers for Disease Control and Prevention, as of August 23 this year, there were 1 120 cases of West Nile virus infection in the United States, which was more than three times the average level in previous years, and 43 of them had died.

"West Nile" struck hard.

Federal health officials in the United States reported on August 22nd that the West Nile virus (WNV) spread by mosquitoes broke out in the United States this year, which was the most serious since it was discovered in the United States in 1999.

1937, this virus was first discovered in the West Nile region of Uganda, Africa, and was named accordingly. Since then, virus infections have occurred in Israel, France, South Africa, the Czech Republic and Russia. 1999, West Nile virus first appeared in the Western Hemisphere, presumably caused by migratory birds. In just a few days, 25 people were infected and 7 people died in Queens, new york, USA.

Since then, the West Nile virus has taken root and sprouted in the United States, officially "settled down", and constantly attacked the city and expanded its territory of aggression. In 2002 and 2003, the West Nile epidemic raged, causing 4 156 infections, 248 deaths, 7,700 infections and 166 deaths respectively. Since 1999, the total number of people who died of the virus in the United States has reached 1200, and the mortality rate is about 3%-5%, among which the morbidity and mortality of the elderly and people with weak immunity are higher.

The West Nile is in full swing this year. At present, only Alaska, Hawaii and Vermont in the United States have not reported confirmed or suspected cases, but this is not the final data.

"The outbreak period of West Nile virus is generally concentrated in mid-August. People often feel unwell after several weeks of infection before going to the hospital and reporting cases. So we estimate that there will be more cases next. " Lyle Peterson, director of the Department of Insect-borne Infectious Diseases of the US Centers for Disease Control and Prevention, said.

The main hosts of West Nile virus are birds and mosquitoes. Mosquitoes bite birds that carry the virus and then spread it to other animals (such as horses and other livestock) and people. The virus can also be transmitted to people through organ transplantation, blood transfusion, breastfeeding and intrauterine transmission, but normal contact between people will not spread the virus.

June 5438 +065438+2003 10, a baby girl born in New York State suffered from congenital brain injury. The researchers believe that this is because her mother was infected with West Nile virus when she was pregnant for three months and passed it on to her through the uterus. This is the first known case of West Nile virus spreading in this way. The baby looked normal at birth, but eye and brain tests showed that her nervous system was severely deformed with brain tissue loss. The US Centers for Disease Control issued a special warning that pregnant women must avoid being bitten by mosquitoes in the summer when mosquitoes are prevalent.

At present, there is no specific drug for West Nile virus, and the related vaccine for protecting human beings has not yet come out. The "West Nile fever" caused by the virus shows cold-like symptoms such as fever, headache, muscle pain, nausea, vomiting, rash and lymphadenopathy, which lasts for 3-6 days. Very few patients will turn to west Nile encephalitis or west Nile meningitis, and in severe cases, it will be life-threatening.

Even if it is cured at that time, the sequelae of West Nile virus will persist for a long time. For example, Mr. Benny, who was infected in southwest Chicago in 2002, has not recovered to the situation before 2003, and his brain is still inflexible and forgetful. Experts believe that only 37% of patients with West Nile virus encephalitis can completely return to normal within one year.

To the relief of infectious disease experts, about 200,000 Americans have been exposed to West Nile virus since 1999. This means that some people in the population are already immune to West Nile virus.

General mobilization of mosquito control

Mosquito breeding season is also the high incidence season of West Nile fever. West Nile virus infection occurred in June-165438+ 10, and peaked in late August. This year, most parts of the United States are experiencing the worst drought since 1895, and the continuous high temperature has aggravated the spread of the West Nile virus epidemic.

Experts believe that although the exact cause of the outbreak of West Nile virus this year is still unclear, it is inevitably related to local climate warming. The unusually warm winter last year, the early arrival of this spring and the hot weather in summer may have created suitable conditions for the spread of West Nile virus.

George Di Ferdinando of New Jersey University of Medicine and Dentistry said, "It was very warm this winter, and more mosquitoes survived, so we saw a sharp increase in the incidence rate." According to the statistics of Texas Department of Health and Human Services, this year, the incidence of West Nile virus in Texas is high, and the infection rate is the highest among all states in the United States, mainly because the hot and humid climate causes mosquitoes to breed everywhere, which intensifies the spread of West Nile virus. 586 cases of infection have been found in the local area, and the death rate is 2 1 person.

Although experts have mastered the source and transmission route of West Nile virus, they still can't fully grasp the initiative in this biochemical war. Due to the uncontrollable nature, people can neither change the humidity of the weather nor control the migration of migratory birds. All they can do is clean up the dead water area and spray pesticides to kill mosquitoes. All over the United States, there is a general mobilization against mosquitoes.

Unlike ordinary arboviruses, which only love one or several carriers, West Nile virus is the arbovirus with the largest number of hosts found at present, and it can survive in at least 36 species of mosquitoes. This has brought great difficulties to disease prevention.

In Dallas, Texas, the hardest hit area, the West Nile virus has been completely broken out, causing nearly 200 infections and 10 deaths. On August 15, the mayor of Dallas declared a state of emergency and authorized aerial spraying of pesticides.

If a city is defined by smell, Dallas used to smell like a steak house, because its air was always full of fried food such as fried chicken legs and fried bacon. Now, it is more like a giant pesticide.

However, despite the death cases and overwhelming pesticide spraying in Dallas, the epidemic did not cause widespread panic among the people as expected. During the day, people still sit in outdoor cafes and restaurants in shorts and T-shirts, drinking coffee and eating leisurely.

Although many cities, including new york, spray pesticides in the air to reduce the number of mosquitoes, there are different voices. Some Dallas residents are increasingly worried that pesticides sprayed in the air may be more harmful than the virus itself. On Change.org's website, more than 65,438+0,700 people signed an online petition asking Dallas officials to stop aerial spraying. The petition describes this measure as ineffective and unsafe, and suspects that it will kill other insects, such as bees and ladybugs. After all, this is the first aerial photography in Dallas since 1966.

At present, no cases of West Nile infection have been found in China, but Liu Qiyong, a professor at China Center for Disease Control and Prevention, who has long been concerned about the virus, said in an interview with the media that on the one hand, because the host of the virus is birds, it can also infect domestic animals such as horses, and the transmission route is extensive, on the other hand, the virus has also broken out in Africa, Europe and America in history, so there is still a risk of introduction in China.