Diarrhoeal diseases - a major cause of child deaths globally
By Dr. Ayesha khan
The eagerly expected Monsoon brings with it the much needed cheer to the face of the Indian farmer and concern in the face of the Indian Doctor. Past experience indicates that the monsoon season is when there is sharp increase in the number of cases of Diarrhoea, Malaria and Dengue.
Among these dieases, Diarrhoeal diseases are a major cause of hospitalizations and child deaths globally. Together they account for approximately one in six deaths among children younger than five years. Of India’s more than 2.3 million annual deaths among children, about 334 000 are attributable to diarrhoeal diseases. Rotavirus is the leading cause of severe diarrhoea in children in developed and developing countries. Two rotavirus vaccines have been shown to be effective against rotavirus and have been licensed in more than 100 countries, including India. Introduction of these vaccines is expected to reduce child mortality by decreasing the incidence of severe diarrhoea and the frequency of death from diarrhoeal disease.
Rotavirus is a genus of double-stranded RNA virus in the family Reoviridae. Nearly every child in the world has been infected with rotavirus at least once by the age of five. Immunity develops with each infection, so subsequent infections are less severe; adults are rarely affected. There are five species of this virus, referred to as A, B, C, D, and E. Rotavirus A, the most common species, causes more than 90% of infections in humans.
The virus is transmitted by the faecal-oral route. It infects and damages the cells that line the small intestine and causes gastroenteritis (which is often called "stomach flu" despite having no relation to influenza). Although rotavirus was discovered in 1973 and accounts for up to 50% of hospitalisations for severe diarrhoea in infants and children, its importance is still not widely known within the public health community, particularly in developing countries. In addition to its impact on human health, rotavirus also infects animals, and is a pathogen of livestock.
Rotavirus is usually an easily managed disease of childhood, but worldwide more than 450,000 children under five years of age still die from rotavirus infection each year, most of whom live in developing countries, and almost two million more become severely ill. In the United States, before initiation of the rotavirus vaccination programme, rotavirus caused about 2.7 million cases of severe gastroenteritis in children, almost 60,000 hospitalizations, and around 37 deaths each year. Public health campaigns to combat rotavirus focus on providing oral rehydration therapy for infected children and vaccination to prevent the disease. The incidence and severity of rotavirus infections has declined significantly in countries that have added rotavirus vaccine to their routine childhood immunisation policies.
Signs and symptoms
Rotavirus gastroenteritis is a mild to severe disease characterised by vomiting, watery diarrhoea, and low-grade fever. Once a child is infected by the virus, there is an incubation period of about two days before symptoms appear. Symptoms often start with vomiting followed by four to eight days of profuse diarrhoea. Dehydration is more common in rotavirus infection than in most of those caused by bacterial pathogens, and is the most common cause of death related to rotavirus infection.
Rotavirus A infections can occur throughout life: the most severe symptoms tend to occur in children six months to two years of age, the elderly, and those with compromised or absent immune system functions. Due to immunity acquired in childhood, most adults are not susceptible to rotavirus; gastroenteritis in adults usually has a cause other than rotavirus, but asymptomatic infections in adults may maintain the transmission of infection in the community.
Diagnosis and detection
Diagnosis of infection with rotavirus normally follows diagnosis of gastroenteritis as the cause of severe diarrhoea. Most children admitted to hospital with gastroenteritis are tested for rotavirus A. Specific diagnosis of infection with rotavirus A is made by finding the virus in the child's stool by enzyme immunoassay. There are several licensed test kits on the market which are sensitive, specific and detect all serotypes of rotavirus A. Other methods, such as electron microscopy and PCR, are used in research laboratories. Reverse transcription-polymerase chain reaction (RT-PCR) can detect and identify all species and serotypes of human rotavirus.
Treatment and prognosis
Treatment of acute rotavirus infection is nonspecific and involves management of symptoms and, most importantly, maintenance of hydration. If untreated, children can die from the resulting severe dehydration. Depending on the severity of diarrhoea, treatment consists of oral rehydration, during which the child is given extra water to drink that contains small amounts of salt and sugar. In 2004, the WHO and UNICEF recommended the use of low-osmolarity oral rehydration solution and zinc supplementation as a two-pronged treatment of acute diarrhoea. Some infections are serious enough to warrant hospitalization where fluids are given by intravenous drip or nasogastric tube, and the child's electrolytes and blood sugar are monitored. Rotavirus infections rarely cause other complications and for a well managed child the prognosis is excellent.
In 1998, a rotavirus vaccine was licensed for use in the United States. The manufacturer, however, withdrew it from the market in 1999, after it was discovered that the vaccine may have contributed to an increased risk for intussusception, a type of bowel obstruction, in one of every 12,000 vaccinated infants. The experience provoked intense debate about the relative risks and benefits of a rotavirus vaccine. In 2006, two new vaccines against rotavirus A infection were shown to be safe and effective in children, and in June 2009 the World Health Organization recommended that rotavirus vaccination be included in all national immunisation programmes to provide protection against this virus.
Epidemiology
Outbreaks of rotavirus A diarrhoea are common among hospitalised infants, young children attending day care centres, and elderly people in nursing homes. An outbreak caused by contaminated municipal water occurred in Colorado in 1981. During 2005, the largest recorded epidemic of diarrhoea occurred in Nicaragua. This unusually large and severe outbreak was associated with mutations in the rotavirus A genome, possibly helping the virus escape the prevalent immunity in the population. A similar large outbreak occurred in Brazil in 1977.
Rotavirus B, also called adult diarrhoea rotavirus or ADRV, has caused major epidemics of severe diarrhoea affecting thousands of people of all ages in China. These epidemics occurred as a result of sewage contamination of drinking water. Rotavirus B infections also occurred in India in 1998; the causative strain was named CAL. Unlike ADRV, the CAL strain is endemic. To date, epidemics caused by rotavirus B have been confined to mainland China, and surveys indicate a lack of immunity to this species in the United States.
Rotavirus C has been associated with rare and sporadic cases of diarrhoea in children, and small outbreaks have occurred in families.
Prevention
Because improved sanitation does not decrease the prevalence of rotaviral disease, and the rate of hospitalizations remains high despite the use of oral rehydrating medicines, the primary public health intervention is vaccination. Two vaccines against Rotavirus A infection are safe and effective in children: Rotarix by GlaxoSmithKline and RotaTeq by Merck. Both are taken orally and contain attenuated live virus. In 2009, the World Health Organization (WHO) recommended that rotavirus vaccine be included in all national immunisation programmes. The incidence and severity of rotavirus infections has declined significantly in countries that have acted on this recommendation. In Mexico, which in 2006 was among the first countries in the world to introduce rotavirus vaccine, diarrhoeal disease death rates dropped during the 2009 rotavirus season by more than 65 percent among children age two and under. In Nicaragua, which in 2006 became the first developing country to introduce a rotavirus vaccine, severe rotavirus infections were reduced by 40 percent and emergency room visits by a half. In the United States, rotavirus vaccination since 2006 has led to drops in rotavirus-related hospitalizations by as much as 86 percent. The vaccines may also have prevented illness in non-vaccinated children by limiting the number of circulating infections.
Rotavirus vaccines are licensed in more than 100 countries, but only 28 countries have introduced routine rotavirus vaccination. International non-governmental organization PATH, the WHO, the U.S. Centers for Disease Control and Prevention, and the GAVI Alliance are working to bring rotavirus vaccines to developing countries, where children face the greatest burden. Through the Rotavirus Vaccine Program and the Accelerating Vaccine Introduction initiative, these groups are partnering with research institutions and governments to reduce child morbidity and mortality from diarrhoeal disease by making a vaccine against rotavirus available for use in developing countries.