What is Dengue? 什么是骨痛热症?

What is Dengue? 什么是骨痛热症?
“骨痛熱症”(Dengue)一詞,源自西班牙語,意指“裝模作樣”,用來形容骨痛熱症急性期,病人因關節疼痛而持有的步態。
骨痛熱症是由骨痛熱症病毒引起,經蚊虫傳播的傳染病,以高熱、皮疹、肌肉及骨關節劇烈酸痛,顏面及眼結膜充血、頸及上胸皮膚潮紅、淋巴結腫大及白細胞減少等症狀為主要特征。
該病多發生在熱帶國家,男女老幼均會得病。全球每年約有超过5000萬人受感染,常見于熱帶和亞熱帶地域,近年骨痛熱症轉趨活躍,影響全球各地。

Dengue fever/dengue haemorrhagic fever

Dengue haemorrhagic fever was first recognized in many Southeast Asian cities in 1956 (Rudnick 1967). Georgetown, Penang Island is the first city with a dengue haemorrhagic fever outbreak in Malaysia in 1962-64 (Rudnick et al. 1965). Dengue fever/dengue haemorrhagic fever is among the highly ranked new and newly emerging infectious diseases in public health and is considered to be among the most important arthropod-borne viral diseases by WHO (WHO 1997). Dengue fever is an acute febrile viral disease and the symptoms presented frequently are inclusive of headaches, bone or joint and muscular pains, rash and leukopenia (WHO 1997). The four major clinical manifestations characterized by the dengue haemorrhagic fever are: high fever, hemorrhagic phenomena, often with hepatomegaly and signs of circulatory failure (in severe cases). Sometimes the patients may experience dengue shock syndrome (DSS) due to plasma leakage and it can be fatal (WHO 1997).
   
​The dengue virus belongs to the family of Flaviviridae. There are four serotypes of dengue virus inclusive of DEN-1, DEN-2, DEN-3 and DEN-4. The type of virus can be distinguished by serological methods. Patients that are infected by either of the dengue viral serotype will produce life-long immunity against reinfection by that same serotype. However, these only provide temporary and partial protection against the other serotypes (WHO 1997). The dengue virus is approximately 50 nm and they share many characteristics with other flaviviruses.

Aedes aegypti is among the most efficient mosquito vectors for arboviruses. This is due to their highly arthrophilic tendency and are in very close contact to humans and often lives indoors (WHO 1997). Aedes mosquitoes are cosmopolitan. Other mosquito species that have been confirmed as dengue vectors includes Ae. albopictus, Ae. polynesiensis and Ae. scutellaris. Among the various ways of combating dengue disease, vector control is the most effective and preventive method (Alias 1995).

Dengue viruses are transmitted to human through the bite of infected Aedes mosquitoes (WHO 1997). Female Aedes need a blood meal to lay eggs. Therefore, dengue viruses are considered as arthropod-borne virus and the DF/DHF are vector-borne diseases. The infected vector mosquito will remain infected for life and is able to transmit the disease during every feeding (WHO 1997). Infected female will also be able to pass the viruses to the next generation, termed as transovarian transmission (WHO 1997, Lee 2000a). Dengue viruses transmitted transovarially have been demonstrated (Lee et al. 1997a, WHO 1997, Lee 2000a), as such, the success in controlling the Aedes larvae is becoming the key factor in preventing the outbreak of the dengue disease.

Up to date, no medication has been proven to be effective for DF/DHF treatment although a vaccine for dengue fever is actively being researched. The only approach to combating DF/DHF at present is in dengue vector control.

常问问答

问: 骨痛熱症有几種?
答:骨痛热症病毒共有四种暨DEN 1, DEN 2, DEN 3 及 DEN 4.
其中3種會導致溢血死亡。所謂的4種,是與血清有關,而不是4種virus。
骨痛热症包括所有的蚊媒传播病毒或疾病都是属于特殊蚊子传播性的。就是说,即使骨痛热症病毒进入其他(除了黑斑蚊)蚊子身上,而这些蚊子如家蚊或虐蚊即使叮咬人们而把骨痛热症病毒传入人体,被叮咬的人民也不会感染骨痛热症的,因为这些蚊子是无法传播骨痛热症。相同的,任何骨痛热症病毒都可以通过白线斑蚊或埃及斑蚊传播给被叮咬的人们。不过,通过不同的蚊子品种,被传播的骨痛热症病毒所带来的影响也不同。比如,通过白线斑蚊,就会感染传统骨痛热症,感染者通常会发烧但是不会溢血,也很少会有致命病列。但是,如果是通过埃及斑蚊传染的话,就很大可能会制溢血症而会致命了。
简单来说,这些病毒所带来的危害都跟黑斑蚊品种有着重大的关系。

问:如果一個人中過第一種骨痛熱症(不是溢血的),他身上就會有抗體,這個人如果再被咬第二次,又不幸是中第二種骨痛熱症,第二種骨痛熱症的virus會與第一種骨痛熱症的抗體產生互相作用,這情況會導致溢血的骨痛熱症。這麼一來,中過骨痛熱症的人,變成很高風險中溢血的骨痛熱症。這個說法正確嗎?
答: 骨痛热症属于病毒,因此人们在感染痊愈后都会终身免疫。但是,因为骨痛热症病毒有四种,如果第二次感染的是另外不同品种的病毒,那么就会出现过度反应的情况。这时候,人们的抗体因为有第一次的经验而会有更大的应对反映,但是又无法有效的应对这不同的病毒而导致危险。如果本身的抗体无法战胜,就会有溢血及致命的情况。即使成功第二次战胜第二品种的骨痛热症病毒,如果第三次受感染第三种病毒,情况会更激烈更危险。人的一生要连过四关而痊愈的,实在是需要非常健壮的体魄。因此骨痛热症到目前为止还是非常危险,而且致命病列不断增加也是因为第二/第三或第四次感染的原故。
过去,因为人们的活动范围没有这么广,所有骨痛热症病毒的传播也是属于固定区域性罢了。所以当地人要感染不同骨痛热症病毒的几率也不高。不过,随着交通之发达,人们的漫游率的上升。不同骨痛热症病毒的流通也变得更广,人们会感染不同品种的几率也提升了很多,因此死亡病列也逐年提升。

FAQ

Q:  How many type of Dengue ?
A:There are four dengue virus cum DEN 1, DEN 2, DEN 3 and DEN 4.
Three of that will lead to haemorrhagic death. This is related to the serum, rather than four kinds of virus.
Dengue fever including all vector borne diseases such as malaria are vector mosquitoes specific. This meant that dengue virus is not able to be transmitted by other mosquitoes other than Aedes mosquitoes. Dengue virus is only able to be transmitted by Aedes Aegypti or Aedes Albopictus. However, different Aedes species will transmit same dengue virus with different dengue fever effect. For example, Aedes albopictus will only transmit classical dengue fever, but Aedes Aegypti will transmit dengue haemorrhagic fever which is fatal.
As conclusion, the effect of dengue virus is very dependent on Aedes species.