China Health Overview

A yellow fever vaccination certificate is required from travellers coming from infected areas. There is a risk of malaria throughout the low-lying areas of the country, and it is recommended that travellers to China seek medical advice before departure. A total of 18 human cases of avian influenza ('bird flu') have been reported from China since November 2005. Twelve of the cases were fatal. Travellers are unlikely to be affected by bird flu, but live animal markets and places where contact with live poultry is possible should be avoided. All poultry and egg dishes should also be thoroughly cooked. Outbreaks of SARS (Severe Acute Respiratory Syndrome) are officially over, but travellers are warned to remain vigilant for this viral disease. The last case occurred in April 2004. Japanese encephalitis has been responsible for the deaths of a number of people in the Shaanxi and Shanxi provinces in northern China, and rabies infects people every year, occasionally causing death. Outbreaks of dengue fever occur. Altitude sickness can occur in the mountainous regions of Tibet, Qinghai, parts of Xinjiang, and western Sichuan. Outside city centres, visitors should only drink bottled water. Western-style medical centres with international staff are available in the major cities and usually accept credit cards. Health insurance is recommended.

Malaria

General considerations: Malaria is a common and life-threatening disease in many tropical and subtropical areas. It is currently endemic in over 100 countries, which are visited by more than 125 million international travellers every year. Each year many international travellers fall ill with malaria while visiting countries where the disease is endemic, and well over 10,000 fall ill after returning home. Fever occurring in a traveller within three months of leaving a malaria-endemic area is a medical emergency and should be investigated urgently. Cause: Human malaria is caused by four different species of the protozoan parasite Plasmodium: Plasmodium falciparum, P. vivax, P. ovale and P. malariae. Transmission: The malaria parasite is transmitted by various species of Anopheles mosquitoes, which bite mainly between sunset and sunrise. Nature of the disease: Malaria is an acute febrile illness with an incubation period of 7 days or longer. Thus, a febrile illness developing less than one week after the first possible exposure is not malaria. The most severe form is caused by P. falciparum, in which variable clinical features include fever, chills, headache, muscular aching and weakness, vomiting, cough, diarrhoea and abdominal pain; other symptoms related to organ failure may supervene, such as: acute renal failure, generalized convulsions, circulatory collapse, followed by coma and death. It is estimated that about 1% of patients with P. falciparum infection die of the disease. The initial symptoms, which may be mild, may not be easy to recognize as being due to malaria. It is important that the possibility of falciparum malaria is considered in all cases of unexplained fever starting at any time between the seventh day of first possible exposure to malaria and three months (or, rarely, later) after the last possible exposure, and any individual who experiences a fever in this interval should immediately seek diagnosis and effective treatment. Early diagnosis and appropriate treatment can be life-saving. Falciparum malaria may be fatal if treatment is delayed beyond 24 hours. A blood sample should be examined for malaria parasites. If no parasites are found in the first blood film but symptoms persist, a series of blood samples should be taken and examined at 6-12-hour intervals. Pregnant women, young children and elderly travellers are particularly at risk. Malaria in pregnant travellers increases the risk of maternal death, miscarriage, stillbirth and neonatal death. The forms of malaria caused by other Plasmodium species are less severe and rarely life-threatening. Prevention and treatment of falciparum malaria are becoming more difficult because P. falciparum is increasingly resistant to various antimalarial drugs. Of the other malaria species, drug resistance has to date been reported for P. vivax, mainly from Indonesia (Irian Jaya) and Papua New Guinea, with more sporadic cases reported from Guyana. P. vivax with declining sensitivity has been reported for Brazil, Colombia, Guatemala, India, Myanmar, the Republic of Korea, and Thailand. P. malariae resistant to chloroquine has been reported from Indonesia. Geographical distribution: The risk for travellers of contracting malaria is highly variable from country to country and even between areas in a country. In many endemic countries of Latin America and the Caribbean, Asia and the Mediterranean region, the main urban areas, but not necessarily the outskirts of towns, are free of malaria transmission. However, malaria can occur in main urban areas in Africa and India. There is usually less risk of the disease at altitudes above 1,500 metres, but in favourable climatic conditions it can occur at altitudes up to almost 3,000 metres. The risk of infection may also vary according to the season, being highest at the end of the rainy season. There is no risk of malaria in many tourist destinations in South-East Asia, Latin America and the Caribbean. Source: WHO.

Japanese encephalitis

Cause: Japanese encephalitis (JE) virus, which is a flavivirus. Transmission: The Japanese encephalitis virus is transmitted by various mosquitoes of the genus Culex. It infects pigs and various wild birds as well as humans. Mosquitoes become infective after feeding on viraemic pigs or birds. Nature of the disease: Most infections are asymptomatic (e.g. cause no symptoms). In symptomatic cases, severity varies; mild infections are characterized by febrile headache or aseptic meningitis. Severe cases have a rapid onset and progression, with headache, high fever and meningeal signs. Permanent neurological sequelae are common among survivors. Approximately 50% of severe clinical cases have a fatal outcome. Geographical distribution: Japanese encephalitis occurs in a number of countries in Asia and occasionally in northern Queensland, Australia. Risk for travellers: Low for most travellers. Visitors to rural and agricultural areas in endemic countries may be at risk, particularly during epidemics of JE. Prophylaxis (protective treatment): Vaccination, if justified by likelihood of exposure. Precautions: Avoid mosquito bites. Source: WHO.

Hepatitis B

Cause: Hepatitis B virus (HBV), belonging to the Hepadnaviridae. Transmission: Hepatitis B is transmitted from person to person by contact with infected body fluids. Sexual contact is an important mode of transmission, but infection is also transmitted by transfusion of contaminated blood or blood products, or by use of contaminated needles or syringes for injections. There is also a potential risk of Hepatitis B transmission through other skin-penetrating procedures including acupuncture, piercing and tattooing. Perinatal transmission may occur from mother to baby. There is no insect vector or animal reservoir. Nature of the disease: Many HBV infections are asymptomatic (e.g. causes no symptoms) or cause mild symptoms, which are often unrecognised in adults. When clinical hepatitis results from infection, it has a gradual onset, with anorexia, abdominal discomfort, nausea, vomiting, arthralgia and rash, followed by the development of jaundice in some cases. In adults, about 1% of cases are fatal. Chronic HBV infection persists in a proportion of adults, some of whom later develop cirrhosis and/or liver cancer. Geographical distribution: Worldwide, but with differing levels of endemicity. In north America, Australia, northern and western Europe and New Zealand, prevalence of chronic HBV infection is relatively low (less than 2% of the general population). Risk for travellers: Negligible for those vaccinated against hepatitis B. Unvaccinated travellers are at risk if they have unprotected sex or use contaminated needles or syringes for injection, acupuncture, piercing or tattooing. An accident or medical emergency requiring blood transfusion may result in infection if the blood has not been screened for HBV. Travellers engaged in humanitarian relief activities may be exposed to infected blood or other body fluids in health care settings. Prophylaxis (protective treatment): Vaccination. Precautions: Adopt safe sexual practices and avoid the use of any potentially contaminated instruments for injection or other skin-piercing activity. Source: WHO.

Hepatitis A

Cause: Hepatitis A virus, a member of the picornavirus family. Transmission: The virus is acquired directly from infected persons by the faecal-oral route or by close contact, or by consumption of contaminated food or drinking water. There is no insect vector or animal reservoir (although some non-human primates are sometimes infected). Nature of the disease: An acute viral hepatitis with abrupt onset of fever, malaise, nausea and abdominal discomfort, followed by the development of jaundice a few days later. Infection in very young children is usually mild or asymptomatic (e.g. causes no symptoms); older children are at risk of symptomatic disease. The disease is more severe in adults, with illness lasting several weeks and recovery taking several months; case-fatality is greater than 2% for those over 40 years of age and 4% for those over 60. Geographical distribution: Worldwide, but most common where sanitary conditions are poor and the safety of drinking water is not well controlled. Risk for travellers: Non-immune travellers to developing countries are at significant risk of infection. The risk is particularly high for travellers exposed to poor conditions of hygiene, sanitation and drinking water control. Prophylaxis (protective treatment): Vaccination. Precautions: Travellers who are non-immune to hepatitis A (i.e. have never had the disease and have not been vaccinated) should take particular care to avoid potentially contaminated food and water. Source: WHO.

Dengue Fever

Cause: The dengue virus - a flavivirus of which there are four serotypes. Transmission: Dengue fever is transmitted by the Aedes aegypti mosquito, which bites during daylight hours. There is no direct person-to-person transmission. Monkeys act as a reservoir host in south-east Asia and west Africa. Nature of the disease: Dengue occurs in three main clinical forms: Dengue fever is an acute febrile illness with sudden onset of fever, followed by development of generalized symptoms and sometimes a macular skin rash. It is known as "breakbone fever" because of severe muscular pains. The fever may be biphasic (i.e. two separate episodes or waves of fever). Most patients recover after a few days; Dengue haemorrhagic fever has an acute onset of fever followed by other symptoms resulting from thrombocytopenia, increased vascular permeability and haemorrhagic manifestations; Dengue shock syndrome supervenes in a small proportion of cases. Severe hypotension develops, requiring urgent medical treatment to correct hypovolaemia. Without appropriate treatment, 40-50% of cases are fatal; with timely therapy, the mortality rate is 1% or less. Geographical distribution: Dengue fever is widespread in tropical and subtropical regions of central and south America and south and south-east Asia and also occurs in Africa; in these regions, dengue is limited to altitudes below 600 metres (2,000 feet). Risk for travellers: There is a significant risk for travellers in areas where dengue fever is endemic and in areas affected by epidemics of dengue. Prophylaxis (protective treatment): None. Precautions: Travellers should take precautions to avoid mosquito bites both during the day and at night in areas where dengue occurs. Source: WHO.

Rabies

Cause: The rabies virus, a rhabdovirus of the genus Lyssavirus. Transmission: Rabies is a zoonotic disease affecting a wide range of domestic and wild animals, including bats. Infection of humans usually occurs through the bite of an infected animal. The virus is present in the saliva. Any other contact involving penetration of the skin occurring in an area where rabies is present should be treated with caution. In developing countries transmission is usually from dogs. Person-to-person transmission has not been documented. Nature of the disease: An acute viral encephalomyelitis, which is almost invariably fatal. The initial signs include a sense of apprehension, headache, fever, malaise and sensory changes around the site of the animal bite. Excitability, hallucinations and aerophobia are common, followed in some cases by fear of water (hydrophobia) due to spasms of the swallowing muscles, progressing to delirium, convulsions and death a few days after onset. A less common form, paralytic rabies, is characterized by loss of sensation, weakness, pain and paralysis. Geographical distribution: Rabies is present in animals in many countries worldwide. Most cases of human infection occur in developing countries. Risk for travellers: In rabies-endemic areas, travellers may be at risk if there is contact with both wild and domestic animals, including dogs and cats. Prophylaxis (protective treatment): Vaccination for travellers with a foreseeable significant risk of exposure to rabies or travelling to a hyperendemic area where modern rabies vaccine may not be available. Precautions: Avoid contact with wild animals and stray domestic animals, particularly dogs and cats, in rabies-endemic areas. If bitten by an animal that is potentially infected with rabies, or after other suspect contact, immediately clean the wound thoroughly with disinfectant or with soap or detergent and water. Medical assistance should be sought immediately. The vaccination status of the animal involved should not be a criterion for withholding post-exposure treatment, unless the vaccination has been thoroughly documented and vaccine of known potency has been used. In the case of domestic animals, the suspect animal should be kept under observation for a period of 10 days. Rabies post-exposure treatment: In a rabies-endemic area, the circumstances of an animal bite, other contact with the animal, and the animal's behaviour and appearance may suggest that it is rabid. In such situations, medical advice should be obtained immediately. Post-exposure treatment to prevent the establishment of rabies infection involves first-aid treatment of the wound followed by administration of rabies vaccine and antirabies immunoglobulin in the case of a bite or exchange of saliva. The administration of vaccine, and immunoglobulin if required, must be carried out, or directly supervised, by a physician. Source: WHO.

SARS

Cause: SARS coronavirus (SARS-CoV) - Virus identified in 2003. SARS-CoV is thought to be an animal virus from an as yet unknown animal reservoir that first infected humans in the Guangdong province of southern China in 2002. Transmission: An epidemic of SARS affected 26 countries and resulted in over 8,000 cases in 2003. Since then, a small number of cases have occurred as a result of laboratory accidents or through animal-to-human transmission (Guangdong, China). Transmission of SARS-CoV is primarily from person-to-person. SARS-CoV is usually spread when symptomatic cases of SARS cough or sneeze expelling infected respiratory secretions either directly onto the mucus membranes (eyes, nose or mouth) of other people or onto nearby surfaces on which the virus may persist for up to several days without cleaning. Transmission of SARS-CoV occurs mainly during the second week of illness which corresponds to the peak of virus excretion in respiratory secretions and stool and when cases with severe disease start to deteriorate clinically. Nature of the disease: Initial symptoms are flu-like and include fever, malaise, muscle aches and pains (myalgia), headache, and shivering (rigors). No individual symptom or cluster of symptoms has proven specific for a diagnosis of SARS. Although fever is the most frequently reported symptom, it may be absent on initial measurement. Cough (initially dry), shortness of breath and diarrhoea may be present in the first week but more commonly reported in the second week of illness. Severe cases develop rapidly progressing to respiratory distress and requiring intensive care. Up to 70% of SARS cases develop diarrhoea which has been described as large volume and watery without blood or mucus. Clinical definition of SARS: A person with a history of fever or a measured fever (≥ 38°C) AND one or more symptoms of lower respiratory tract illness (cough, difficulty breathing, shortness of breath) AND radiographic evidence of lung infiltrates consistent with pneumonia or Acute Respiratory Distress Syndrome (ARDS), OR autopsy findings consistent with the pathology of pneumonia or ARDS without an identifiable cause. No alternative diagnosis can fully explain the illness. Geographical distribution: The distribution is based on the 2002-2003 epidemic. The disease appeared in November 2002 in the Guangdong province of southern China. This area is considered as a potential zone of re-emergence of SARS-CoV. Other countries/areas in which chains of human-to-human transmission occurred after early importation of cases were Hong Kong Special Administrative Region and Taiwan in China, Toronto in Canada, Singapore and Hanoï in Viet Nam. In other countries, imported cases did not lead to local outbreaks. Risk for travellers: Currently, no areas of the world are reporting person-to-person transmission of SARS. Since the end of the global epidemic in July 2003, six cases of SARS have been reported globally - two from laboratory accidents (Singapore and Taiwan) and four in southern China in whom the source of infection remains undetermined although there is circumstantial evidence of animal-to-human transmission. Should SARS re-emerge in epidemic form, the World Health Organisation (WHO) will provide guidance on the risk of travel to affected areas. Travellers should stay informed about current travel recommendations. However, even during the height of the 2003 epidemic, the overall risk of SARS-CoV transmission to travellers was low. Prophylaxis (protective treatment): None. Precautions: Follow travel recommendations if any are issued by WHO. Frequent hand washing. Source: WHO.

Typhoid fever

Cause: Salmonella typhi, the typhoid bacillus, which infects only humans. Similar paratyphoid and enteric fevers are caused by other species of Salmonella, which infect domestic animals as well as humans. Transmission: Infection with typhoid fever is transmitted by consumption of contaminated food or water. Occasionally direct faecal-oral transmission may occur. Shellfish taken from sewage-polluted beds are an important source of infection. Infection occurs through eating fruit and vegetables fertilized by night soil and eaten raw, and milk and milk products that have been contaminated by those in contact with them. Flies may transfer infection to foods, resulting in contamination that may be sufficient to cause human infection. Pollution of water sources may produce epidemics of typhoid fever, when large numbers of people use the same source of drinking water. Nature of the disease: Typhoid fever is a systemic disease of varying severity. Severe cases are characterized by gradual onset of fever, headache, malaise, anorexia and insomnia. Constipation is more common than diarrhoea in adults and older children. Without treatment, the disease progresses with sustained fever, bradycardia, hepatosplenomegaly, abdominal symptoms and, in some cases, pneumonia. In white-skinned patients, pink spots (papules), which fade on pressure, appear on the skin of the trunk in up to 50% of cases. In the third week, untreated cases develop additional gastrointestinal and other complications, which may prove fatal. Around 2-5% of those who contract typhoid fever become chronic carriers, as bacteria persist in the biliary tract after symptoms have resolved. Geographical distribution: Worldwide. The disease occurs most commonly in association with poor standards of hygiene in food preparation and handling and where sanitary disposal of sewage is lacking. Risk for travellers: Generally low risk for travellers, except in parts of north and west Africa, in south Asia and in Peru. Elsewhere, travellers are usually at risk only when exposed to low standards of hygiene with respect to food handling, control of drinking water quality, and sewage disposal. Prophylaxis (protective treatment): Vaccination. Precautions: Observe all precautions against exposure to foodborne and waterborne infections. Source: WHO.