Dengue crisis worsens as disease spreads north

by Michael Woodhead
China is now experiencing its worse outbreak of dengue fever in two decades, with almost 1000 cases a day being recorded in south China, and the infection spreading as far north as Henan.
Outbreaks of the serious infection spread by the Aedes mosquito are centred around Guangdong, where almost 43,000 cases have been recorded this year.
However, the disease is now affecting other parts of China, including  Zhejiang, Fujian, Yunnan and Guangxi, according to the National Health and Family Planning Commission (NHFPC).
"The outbreak of dengue fever this year is the worst in China since 1995, when 6,812 cases were recorded," according to Qin Chengfeng, a researcher with the Chinese Academy of Military Medical Sciences.
Alarm bells are ringing because the infection has also been reported as far north as Henan, half way between Shanghai and Beijing. Researchers say this is the first time the disease has been seen so far from the traditional areas of south China. Infectious disease experts said there were more than 50 cases of dengue fever reported in Shenhou township, presumably imported by migrant workers who had been in south China and Laos. They said the findings should act as a warning that the disease is spreading rapidly within China.
Other experts have attributed the spread of dengue to changing weather patterns, pointing to high rainfall that encourages the breeding of the Aedes mosquito.

China has its first non-imported dengue outbreak in a decade

by Michael Woodhead
Last year, Yunnan experienced an explosive outbreak of  dengue fever spread by mosquitoes.

This was a strange and worrying phenomenon because Yunnan has been dengue free for many years. China has had a few outbreaks of dengue in recent years but they tend to have been in south eastern provinces such as Guangdong, and they are usually related to imported dengue fever. The infection is not endemic to Yunnan.

However, in 2013 health workers in Xishuangbanna had to deal with a huge outbreak of this often severe, life-threatening disease. There were 1245 cases of which 136 patients were hospitalised and 70 were classified as severe cases. The symptoms included severe haemorrhage (including massive vaginal and gastrointestinal bleeding), severe plasma leakage (such as pleural effusion, ascites, or hypoproteinaemia), and organ failure. Twenty of the cases  deteriorated to shock.

In an analysis of the outbreak published in the International Journal of Infectious Diseases, Dr Zhang Fuchun of the Guangzhou 8th People's Hospital say the dengue fever was caused by a new virulent strain of the virus known as serotype 3 (DENV-3). But the main reason for the severity of the outbreak was that the infection was spread  more rapidly by a different type of mosquito - Aedes. aegypti. The usual type of mosquito seen in Yunnan is known as Aedes albopictus, and dengue caused by this species tends to be milder and short lived. The researchers say the 'double whammy' of a new strain of dengue and a new strain of mosquito combined to "carries a high risk for a severe epidemic and endemicity" in an area that was until recently dengue free.

Tropical diseases in China: one down, ten to go

by Michael Woodhead
China has eliminated one tropical disease - lymphatic filiarisis - but has ten others that are still affecting millions of people and some of which are becoming endemic again, according to a new report.
The good news from a review of China's tropical diseases published in The Lancet Infectious Diseases is that the country is on track to eradicate five major diseases (schistosomiasis, leishmaniasis, leprosy, rabies and trachoma) in the next five to ten years.  However, the not-so-good news is that some diseases are still uncontrolled and affect millions of people in poorer provinces of the south and west. The most problematic diseases are dengue fever, food-borne parasitic diseases such as liver flukes and Echinococcosis, according to the article by researchers at the Wuxi branch of the Ministry of Health. Professor Yang Guo Jing and colleagues from the Key Laboratory for Parasitic Diseases say that lymphatic filiarisis was eliminated from China in 2007 after a long campaign to remove it from 16 provinces by using mass drug administration techniques.
Tropical diseases in the 'near-elimination' stage include schistosomiasis, which has been successfully controlled in most parts of the country and numbers reduced from 12 million to 287,000 in 2011. The disease is spread by cattle and water buffalo, and thus changes in farming techniques are needed to help eliminate the disease. Similar improvements in control have been seen for leishmaniasis, the sandfly-spread protozoal infection which used to be common around the Yangtze river basin but now affects only about 2500 people a year. The bacterial infection trachoma that causes blindness is also close to elimination due to implementation of mass campaigns that apply WHO strategies such as facial cleanliness. Rabies has also been controlled, but still causes 2000-3000 cases a year. Immunisation of 70% of dogs at risk should break the cycle of infection, but currently only about 20% are vaccinated. Leprosy was reported to affect about 6000 people in China in 2010, of which about 1300 were new cases. Better surveillance and multi-drug treatment regimens should help eradicate the infection by 2020, the report suggests.
China has has less success with soil-transmitted helminthiasis, and there are about 85 million Chinese affected by roundworm and whipworm. De-worming of schoolchildren seems to have only modest efficacy, and so new strategies such as curbs on the use of human waste as fertiliser are needed, the report says.
The most problematic tropical diseases for China include dengue fever, with outbreaks of the mosquito-borne infection rapidly emerging as a major public health problem. Climate change is worsening the problem, which requires better monitoring and mosquito management strategies as there is no drug or vaccine for the disease.
Another major problem tropical disease for China are the food-borne parasitic zoonoses, such as liver flukes, lung flukes, and other trematodes that may be transmitted by fish, snails and freshwater plants. There are tens of millions of cases in China, which has the dubious honour of having 80% of the 15 million cases globally. New programs are needed to identify high risk disease areas and to address transmission of infection through occupational risk (eg farmers) and also consumption of high risk foods.
Control of these many tropical diseases will require huge  resources to build and design  programs specific for each disease and the high risk locations and populations they affect, the authors conclude.

China medical news for Thursday 30 January

Blood lead levels still hazardous for Chinese children
Blood lead levels for children have decreased in recent years but are still at unhealthy levels, a study carried out in 11 cities has found. The blood sampling survey of 12 000 children under six years of age found that average blood lead levels dropped by 16% (from 46μg/L in 2004 to 39μg/L in 2010). The prevalence of elevated blood lead levels dropped by 87% (from 9.8% in 2004 to 1.3% in 2010). Factors associated with high blood levels included eating popcorn, chewing fingernails, sucking fingers, being cared for at home or at a boarding nursery, the study in the World Journal of Pediatrics found.

Rise in China's caesarean rates 'alarming'
The overuse of cesareans is rising alarmingly in China and has become a real public health problem, a review by researchers in Beijing has concluded. The current national caesarean rate is near 40%, and there has been a rapid rise of cesarean sections in recent years, say researchers from the School of Public Health at Peking University. Nonclinical factors such as financial incentives for hospitals were considered as the main drivers fueling the rise of cesareans. However the change in health services to focus on specialised care and marginalizing primary care have also played a role, they say in the International Journal of Women's Health.  

Dengue fever changes in Guangdong
The pattern of dengue fever outbreaks in Guangdong is changing, infectious disease specialists have found. The disease appears to be becoming endemic although outbreaks are caused by the milder types of dengue, researchers report. The prevalance varies between 2-5% and serotypes are now more varied, according to the study in PLOS One.

Puberty arrives earlier for Chinese girls
The age of onset of puberty is now at least a year earlier for Chinese girls compared to those of 1984, a study from the Capital Institute of Pediatrics, Beijing, has found. The research in the World Journal of Pediatrics found that the age of onset of puberty for urban girls had decreased by 4.2 months per decade, and that of rural girls by 9.6 months per decade from 1980 to 2004.

Fish pedicures a hepatitis risk
Aqua pedicures where tiny fish nibble away at dead skin on bathers feet may spread blood diseases such as HIV and hepatitis B, a Ningbo newspaper says. Dr Wang Jiahua, a dermatologist at a local hospital, said there were risks of infection, citing a patient whose legs became hot and swollen days after his first fish pedicure.He suggested a one month interval between fish pedicures and antibiotic ointment to protect skin where wounds are found.

Dengue fever controls insufficient to prevent outbreaks in Guangdong

Dengue is spread from infected visitors by Aedes mosquitoes that thrive in Guangzhou

by Michael Woodhead
Dengue fever outbreaks in Guangdong are not due to endemic infection but are being triggered by imported cases that slip through inadequate border controls and poor local hospital surveillance, researchers have found.
Despite fears that dengue was re-emerging as an endemic disease in Guangdong, researchers from the Guangzhou Center for Disease Control and Prevention have traced the source of three recent outbreaks in the region to travellers arriving in Guangzhou from Vietnam, India and Tanzania.
A 2009 outbreak was straced to a Chinese man who returned from a trip to Vietnam, the report in PLOS One. Two other outbreaks in 2009 and 2010 were traced to visitors from India and Tanzania, the latter resulting in almost  80 cases of the disease in the city. Using genetic analysis of the dengue virus, the researchers showed that the strains were not like the endemic strain seen previously in China but were similar to strains seen internationally.
The outbreaks of dengue infections mostly occurred following the monsoon season, when the climatic factors (temperature and humidity) remained conducive for Aedes mosquito breeding. Most of the patients were in the age group of 21–50 years, which is contrary to the popular belief that dengue is a paediatric disease.
The outbreaks occurred because the dengue fever cases were initially misdiagnosed, which is understandable as initial symptoms are often non-specific and viraemia may be below detectable levels. Outbreaks of dengue in Guangzhou are also promoted by Cantonese habit of culturing water plants and keeping water for watering flowers, and environment were suitable for the breeding of  dengue carrying Aedes albopictus mosquitoes.  Also, there is a lack of local self-awareness of the need to protect against dengue, the researchers say.
The researchers are critical of the half hearted measures taken by local government to identify imported dengue cases and reduce the local transmission.
The Guangdong dengue control program includes a network of rapid diagnostic laboratories, and fever screening at international airports using infrared thermal scanners. However, febrile passengers suspected of having dengue virus infection are not detained at the airport nor required to complete the “Dengue Survey Form”, and only provided with a mosquito net, which is rarely used.
"These findings underscore the importance of early detection and case management of imported case in preventing large-scale dengue epidemics among indigenous peoples of Guangdong," they conclude.
Source: PLOS One