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Seasonal sickness

Jyotsna Jagai, born more than 20 summers ago to an Indian couple from Andhra Pradesh settled in the US, shares more than her ancestry with children born and raised in India — susceptibility to a disease whose affliction is nearly universal. Rotavirus infections, which cause extreme diarrhoea and dehydration, spare none. Almost all human beings suffer an attack, except the lucky few born after rotavirus vaccines arrived on the scene a few years ago.

The difference, however, is that it kills children in much larger numbers in resource poor settings of developing countries compared to first world nations where nutrition is not a problem. As common as flu, rotavirus infections kill over half a million children below the age of five every year across the world. And every fourth victim is from India.

Over the years, scientists have observed a weather-related pattern in rotavirus attacks. In temperate climate, the infection peaks in colder months. If such links to weather could be established in the tropics, where the infection is more fatal, many young lives could be saved.

So Jagai set out to look for a seasonal pattern of rotavirus infections in tropical countries. Her earlier PhD work under Elena Naumova of the department of civil and environmental engineering at Tufts University in the US came in handy. For her doctorate, Jagai, who is currently a postdoc at the US Environmental Protection Agency, developed tools that identify meteorological signatures associated with seasonal peaks in cryptosporidiosis, a diarrhoeal disease caused by protozoa.

“Scientists have been trying to understand the seasonal patterns of various diseases for quite some time. However, with changes in meteorological conditions and patterns owing to climate change, there has been a resurgence of interest in understanding these impacts on human health,” Jagai told KnowHow.

For the rotavirus study, the Tufts team partnered with Gagandeep Kang, a microbiologist at the Christian Medical College in Vellore and her team. Kang has been studying rotavirus infections in India for more than two decades.

The scientists analysed 40 previous studies on rotavirus outbreaks in South Asian countries such as India, Pakistan, Bangladesh, Sri Lanka and Myanmar in the last 22 years. The incidence data retrieved were correlated with temperature, precipitation and vegetation cover data. The analysis showed that a decrease in temperature and vegetation cover and an increase in rainfall are predictably linked to rotavirus outbreaks. “We found that rotavirus is sensitive to seasonal patterns that are defined as a combined effect of temperature and precipitation,” says Naumova. The findings of the study appeared in the journal PLoS One on May 31.

Jyotsna Jagai

Understanding the impact of the weather on rotavirus infections offers a number of benefits to developing countries, says Naumova, one of the authors of the study. “The public and health professionals can be better prepared by timely reinforcing various preventive measures, like vaccination and personal hygiene. Medical personnel can be better trained in recognising infections…… (and) by knowing the timing of high risk, the limited resources can be strategically allocated when they are most needed,” she told KnowHow.

“It is very well known that rotavirus infections are more prevalent in winter. That is why it is called winter diarrhoea. It has nothing to do with sanitation, unlike cholera. This explains why it is prevalent all over the world, including developed countries. But since children in the West are better nourished, the mortality there is very, very low,” says G. Balakrish Nair, executive director of Translational Health Science and Technology Institute, Gurgoan.

Nair says the study will help forecast rotavirus outbreaks in regions in India that do not have a pronounced winter, say, the coastal areas. “Knowing the seasonality of an infection helps as it allows you to be better prepared,” says Nair, who studied diarrhoeal diseases for nearly 30 years. If an outbreak is expected, children in that area can be vaccinated. The vaccines may not prevent infection but they do reduce its severity.

Rotavirus vaccines, developed by two global pharmaceutical giants, are available in India, but they are expensive. Each dose of the rotavirus currently costs about Rs 1,000, says K. Ramalingam, a paediatrician at Max Balaji Hospital in east Delhi. But an international private-public health partnership, GAVI Alliance, has promised to supply rotavirus vaccines to the Indian public health programme at a substantially reduced rate. “This may help us to reach out to the needy,” hopes Ramalingam.