(P <0.01, P <0.001). and Phenylpiracetam 5160 years groups, the risk of ADE in DENV-4 contamination was positively associated with the extension of convalescent phase, and the odd ratio was higher than other groups. With the recovery period lengthened, the risk of secondary contamination with DENV-1 and DENV-2 was reduced. Our results offer essential experimental data for risk prediction of severe dengue in hyper-endemic dengue areas, and provide crucial scientific insight for the development of effective dengue vaccines. Keywords:Dengue computer virus (DENV), Seroepidemiology, Neutralizing antibody (NAb), Cross-reactive antibody, Antibody dependent enhancement (ADE) == Highlights == The positive rates of DENV-specific IgG were 98.4% and 82.8% in four-year and six-year sera. The geometric mean titer of NAb to DENV-3 decreased from 1:155.35 to 1 1:46.66. ADE risk in secondary contamination with DENV-1 and -2 was reduced in consecutive sera. ADE risk in secondary contamination with DENV-4 was raised in 3140, 5160 years groups. == 1. Introduction == Dengue is the most important mosquito-borne febrile illness caused by any one of four unique antigenically related dengue computer virus serotypes (DENV-14), which are single positive-strand RNA viruses belonging to the familyFlaviviridae, genusFlavivirus(Simmons et al., 2012). DENV is mainly transmitted byAedes aegyptiandAedes albopictus.It is widely prevalent in more than 100 countries in tropical and subtropical areas (Tan et al., 2019). The clinical classification Phenylpiracetam of DENV-infected disease includes two categories: dengue fever (DF), and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) that is defined as severe dengue (Lin et al., 2017). The majority of DF cases are self-limited febrile illness, which is characterized by high fever, headache, rash, myalgia, and arthralgia (Screaton et al., 2015). However, severe dengue is usually more potentially fatal than DF, and usually leads to plasma leakage, severe bleeding or severe organ impairment (WHO, 2009). As World Health Business (WHO) reported, up to 400 million people get infected with dengue annually. Approximately 22,000 people die from severe dengue, placing a heavy burden on global public health. Today, severe dengue has become a leading cause of hospitalization and death among people in most Asian and Rabbit Polyclonal to Chk2 (phospho-Thr387) Latin American countries. In Asia, after the Second World War, the incidence of dengue has grown dramatically in South-East Asia, particularly in Vietnam and Thailand. And severe dengue Phenylpiracetam was first acknowledged in the 1950s in the Philippines and Thailand (Pinheiro and Corber, 1997;Tavano and Boasso, 2014). After the 20th century, the geographical distribution of dengue transmission was spanning westward from Southeast Asian countries to Sri Lanka, India, Pakistan and other regions, and eastward to China. In 1978, dengue case was first reported in Guangdong Province of China following with an increasing pattern of the annual number (Guo et al., 2015;Lin et al., 2020). In mainland, the prevalence of DF expanded from the southeastern coastal areas to the northern and western regions subsequently (Lin et al., 2020). Yunnan Province is located in southwest China and geographically bordering Myanmar, Laos and Vietnam where dengue is usually endemic. Additionally, abundant rainfall, humid environment and the tropical and subtropical monsoon climate favour mosquito breeding which provides suitable conditions for dengue outbreaks in Yunnan. In Yunnan Province, the first outbreak of dengue occurred in 2008 and involved 56 reported cases (Wu et al., 2010). In recent years, the number.