About 20,000 Indians are hospitalised every year for dengue infections, according to government figures. Yet a new study claims that the actual number of Indians affected by dengue could be six million a year, nearly 300 times greater than the government figures suggest.
The study was funded through a contract with vaccine maker Sanofi Pasteur, which has a dengue vaccine that is in the late stages of clinical development. However, the study’s authors claim that the company was not involved in the actual research or preparation of the study.
The difficulty in determining the prevalence of dengue cases in India arises because of the slippery nature of the infection. The stark reality is that many people in India have probably had it, but just not known about it.
Four strains
Dengue is transmitted to humans from the bite of a mosquito carrying one of the four strains of the virus. “There are four strains, so natural infection can happen at least four times,” said Dr Narendra K Arora, executive director of the International Clinical Epidemiology Network, and co-author of the study. “Given that there are such a large number of infections annually, almost six million per year, at least at some point in your life it is extremely likely that you would be exposed to at least one strain.”
The effects of being infected by only one strain of the virus are relatively minor, with symptoms like mild fever, severe headache and muscle and joint pain. The World Health Organisation says that aside from seeing a doctor, people with this kind of dengue fever should rest, drink plenty of fluids, and take paracetamol. But the real danger comes from cases of severe dengue (also known as dengue hemorrhagic fever), which affects mainly children and involves a potentially lethal combination of symptoms like fever, persistent vomiting, bleeding and breathing difficulty. The danger is exacerbated further by the fact that there is currently no vaccine for the disease.
“Usually the first episode is a mild episode,” said Dr Arora. “When exposed to a second strain your response is likely to be more severe,”
Discrepancy in reporting
Calculating the real spread of dengue offers a lesson on the limitations faced by public health researchers today. On the one hand, only about 1% of dengue cases advance to life-threatening stage, which must be a factor in the government’s low assessments. At the same time, issues with reporting and monitoring of diagnosed cases can often lead to discrepancies.
“The issue with many of the probable cases is that we cannot be sure if we are handling dengue or other forms of fever,” said Dr AC Dhariwal, director of the Ministry of Health’s National Vector Borne Disease Control Programme. “We have this problem of distinguishing between probable cases and confirmed cases in dealing with malaria also.”
The study’s authors argue that difficulty in reaching a hard number for confirmed cases should not preclude officials from working to address the real gaps in national public health monitoring systems. The study was the first to use systematic empirical data to estimate the burden and costs of dengue on India, and was led by researchers from Brandeis University, the INCLEN Trust International in Delhi, and the Indian Council of Medical Research’s Centre for Research in Medical Entomology in Madurai, Tamil Nadu.
Their findings do shine light on the discrepancies that exist between confirmed and prospective cases of dengue. The Health Ministry seems to be taking the findings seriously. As Dr. Dhariwal said, “We are aware of the facts that the study puts forth, and are taking them into account.”
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The study was funded through a contract with vaccine maker Sanofi Pasteur, which has a dengue vaccine that is in the late stages of clinical development. However, the study’s authors claim that the company was not involved in the actual research or preparation of the study.
The difficulty in determining the prevalence of dengue cases in India arises because of the slippery nature of the infection. The stark reality is that many people in India have probably had it, but just not known about it.
Four strains
Dengue is transmitted to humans from the bite of a mosquito carrying one of the four strains of the virus. “There are four strains, so natural infection can happen at least four times,” said Dr Narendra K Arora, executive director of the International Clinical Epidemiology Network, and co-author of the study. “Given that there are such a large number of infections annually, almost six million per year, at least at some point in your life it is extremely likely that you would be exposed to at least one strain.”
The effects of being infected by only one strain of the virus are relatively minor, with symptoms like mild fever, severe headache and muscle and joint pain. The World Health Organisation says that aside from seeing a doctor, people with this kind of dengue fever should rest, drink plenty of fluids, and take paracetamol. But the real danger comes from cases of severe dengue (also known as dengue hemorrhagic fever), which affects mainly children and involves a potentially lethal combination of symptoms like fever, persistent vomiting, bleeding and breathing difficulty. The danger is exacerbated further by the fact that there is currently no vaccine for the disease.
“Usually the first episode is a mild episode,” said Dr Arora. “When exposed to a second strain your response is likely to be more severe,”
Discrepancy in reporting
Calculating the real spread of dengue offers a lesson on the limitations faced by public health researchers today. On the one hand, only about 1% of dengue cases advance to life-threatening stage, which must be a factor in the government’s low assessments. At the same time, issues with reporting and monitoring of diagnosed cases can often lead to discrepancies.
“The issue with many of the probable cases is that we cannot be sure if we are handling dengue or other forms of fever,” said Dr AC Dhariwal, director of the Ministry of Health’s National Vector Borne Disease Control Programme. “We have this problem of distinguishing between probable cases and confirmed cases in dealing with malaria also.”
The study’s authors argue that difficulty in reaching a hard number for confirmed cases should not preclude officials from working to address the real gaps in national public health monitoring systems. The study was the first to use systematic empirical data to estimate the burden and costs of dengue on India, and was led by researchers from Brandeis University, the INCLEN Trust International in Delhi, and the Indian Council of Medical Research’s Centre for Research in Medical Entomology in Madurai, Tamil Nadu.
Their findings do shine light on the discrepancies that exist between confirmed and prospective cases of dengue. The Health Ministry seems to be taking the findings seriously. As Dr. Dhariwal said, “We are aware of the facts that the study puts forth, and are taking them into account.”
