07 May 2008

Olympic virus

Mikhail Alekseev, MednovostiThe outbreak of enterovirus infection recorded in China in early March continues to spread across the map of the country.

According to the latest data, the number of sick children exceeded 12 thousand, 65 patients were identified in the Jinlin province bordering the Russian Federation. The number of victims of infection remains unchanged – at the moment, 26 dead children are known, the vast majority of whom lived in Fuyang city (Anthoi Province in southeastern China).

In the Russian media, enterovirus-71 (EV71), which caused most of the diseases and the vast majority of deaths, is called "unknown", "mysterious" and even "deadly".  However, there is nothing mysterious about this disease, and the mortality rate among children affected by it does not exceed the rates of other, no less common infections.   

The first representatives of the enterovirus genus were isolated by American researchers in the late 40s - early 50s of the last century. As you can understand from the name, this type of virus is able to multiply in the intestine, but they pose the greatest danger to the central nervous system of the patient.

Enteroviruses belong to the picornavirus family, named after the words pico (very small) and RNA (RNA). They include 67 pathogenic serotypes for humans: 3 types of polio viruses, 23 types of Coxsackie A viruses, 6 types of Coxsackie B viruses, 31 types of ESNO viruses and 4 more types of enteroviruses 68-71.

In approximately 85 percent of cases, enterovirus infections are asymptomatic, in 12-14 percent of patients they are diagnosed as mild viral fevers. Severe course, accompanied by meningitis, encephalitis and other dangerous complications, differ from 1 to 3 percent of cases of enterovirus infections.

Most of the victims of enteroviruses are children under the age of 7. Representatives of older age groups are protected from them by immunity – this is due to the almost ubiquitous prevalence of enteroviruses.

Infection with enteroviruses occurs mainly by fecal-oral route: through dirty hands, unwashed vegetables and untreated water. It is impossible to exclude the airborne method of transmission, but its role in the spread of infection is in any case small.  In this regard, the main method of preventing outbreaks of enterovirus infection is careful compliance with sanitary and hygienic standards and monitoring of new cases of diseases in nurseries, kindergartens, hospitals and schools.

The main "hero" of recent publications, enterovirus-71, is well known to infectious disease specialists. In the last decades of the last century, outbreaks of neuroinfection caused by them were recorded in the USA, Australia, Sweden and Japan (1969-1973), as well as in Bulgaria (1975), Hungary (1976), Malaysia (1997), Taiwan (1998) and Singapore (1999). Cases of the disease in Southeast Asia were characterized by characteristic signs that are now observed in China:  first of all, this is acute pulmonary edema syndrome – one of the main causes of death of patients.

In the 70s of the last century, Soviet scientists created a live inactivated vaccine against enterovirus-71. In 1975, after an outbreak of infection in Bulgaria, Bulgarian children were vaccinated with this drug en masse. However, due to the wide variety of enteroviruses, vaccination of such infections is considered ineffective.

It is worth noting that the subtropical climate zone, covering a significant part of the territory of China, is a zone of year-round circulation of enteroviruses. In this regard, there is nothing unexpected in the spring outbreak of morbidity. Under normal conditions, most cases of enterovirus infection occurring with minimal complications remain undiagnosed, since it is possible to determine the causative agent of the disease only by the results of laboratory tests.

This is what Hans Thredson, the head of the Chinese branch of the WHO, tried to bring to the world community. "We are dealing with a common childhood disease, outbreaks of which regularly occur in Singapore, Vietnam and various parts of China. The number of patients will increase, but there is no reason for alarm," he told reporters.

Indeed, after China, neighboring countries reported outbreaks of enterovirus infection. For example, Vietnam has reported about 400 cases since the beginning of the year, and Singapore – about 9 thousand. It is difficult to say how much these figures exceed the annual average.

After reports of the first cases of infection in China's border areas with Russia, Rospotrebnadzor announced stricter sanitary control at the Russian-Chinese border, as well as increased measures to monitor enterovirus infections in the Russian Federation. However, according to Gennady Onishcheko, there are no plans to close the border with China yet. 

The reason for the increased attention to the quite predictable seasonal rise in morbidity is obvious: in preparation for the Summer Olympics, Chinese officials decided to approach the infectious scourge with all seriousness. A number of Fuyang doctors, who allegedly reported cases of infection too late, have already been subjected to disciplinary penalties, and a state of emergency has been imposed in the city itself. The population of Anhui Province was warned that the concealment of patients will henceforth be severely punished by the authorities. Similar measures have been introduced in other areas affected by the "epidemic".

Of course, the next state campaign will bring only benefits to sick Chinese children: timely diagnosis will save many of them from serious complications and even death. The Chinese authorities, in turn, will receive on the eve of the Olympics the most complete statistics on the incidence of enterovirus infections in the entire history of the country.

Portal "Eternal youth" www.vechnayamolodost.ru07.05.2008

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