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Learn how to differentiate the symptoms of dengue and leptospirosis

For just over a month, Rio Grande do Sul has suffered the consequences of flooding resulting from the heavy rains that hit the state at the end of April. In addition to the problems with the destruction of cities and infrastructure, having thousands of people homeless and hundreds of deaths, the people of Rio Grande do Sul still need to deal with the spread of diseases that spread more easily in scenarios like this, especially the leptospirosis and the dengue . Both have very similar symptoms, which can make correct diagnosis difficult. How to differentiate them?

Leptospirosis is caused by bacteria of the genus Leptospira and transmission occurs through contact with the urine of contaminated rats. In the case of floods, the simple contact of the skin and mucous membranes with dirty water and mud can be enough to cause infection. The first symptoms are a high fever (above 38oC), which starts suddenly, associated with chills, headaches and muscle pains (mainly in the calf region), lack of appetite, nausea and vomiting and red eyes. It is considered by the World Health Organization (WHO) to be a neglected and underreported disease: the estimate is that, every year,500 thousand new casesoccur throughout the world, with mortality rates ranging from 10 to 70% in severe cases.

“Leptospirosis is a notifiable disease throughout the national territory. It must be done as soon as there is suspicion, both in cases of outbreaks and a single case, and as soon as possible, so that epidemiological surveillance actions can be initiated. These actions aim to control the outbreak to prevent more people from developing the disease. In catastrophe situations like the one in Rio Grande do Sul, the entire health system is on alert for suspected cases”, explains Emy Akiyama Gouveia, infectious disease specialist at Hospital Israelita Albert Einstein.

Dengue fever is transmitted through the bite of a female mosquito. Aedes aegypti. Symptoms appear after three to five days and begin with a sudden high fever (between 38º and 40ºC), accompanied by headaches, pain in the joints and behind the eyes, prostration, lack of appetite and nausea. The condition worsens if the person still has red spots on the body and bleeding from the mucous membranes (a sign that there is a decrease in platelets). The mosquito has adapted to the urban environment and reproduces easily, including in stagnant water with organic matter – as is currently the case in the South Region.

An important detail, highlights the infectious disease specialist at Einstein, is that the incubation period for leptospirosis can be long (reaching 30 days, although the average is seven to 14 days) and contamination can also occur directly, through ingestion of food that came into contact with contaminated urine.

“Therefore, there may be situations in which the individual did not come into direct contact with flood water, but ends up developing the infection. In catastrophe situations involving floods, food safety is critical, as contamination can occur due to inadequate storage conditions and the proliferation of rodents in the area”, warns Gouveia.

Correct diagnosis is essential

As the two diseases present very similar signs that can be confused, it is important to seek medical attention and perform the test to confirm the diagnosis . “There is a critical point: in the epidemiological situation that Rio Grande do Sul is facing, the two infections can coexist in the patient. That is why it is so important that people seek medical attention when faced with any suggestive symptom, to be able to rule out serious conditions”, advises the doctor.

The diagnosis of leptospirosis is made by collecting a blood sample to assess the presence of antibodies. It is also possible to carry out direct research on the bacteria, culture or molecular biology examination with the search for the presence of DNA. According to Gouveia, other non-specific tests help to assess the severity, such as blood tests to evaluate coagulation, kidney and liver and the electrocardiogram, among others, which can be indicated according to the patient’s clinical condition.

To confirm dengue fever, the patient’s clinical condition is taken into account and, in some cases, laboratory tests are carried out, such as a blood count, a search for antibodies produced against the virus, a search for antigens and biochemical tests.

Leptospirosis can result in asymptomatic, mild (which only requires outpatient treatment) or severe conditions, with impairment of the liver (yellowing skin), kidneys, kidney failure (possibly requiring hemodialysis), lungs and of the nervous system. “In the case of leptospirosis, the sooner antibiotic treatment is started, the better. In milder cases, the patient can receive the medication at home, orally. In severe cases, intravenous antibiotics must be used”, advises Gouveia.

Researchers at the Butantan Institute, in São Paulo, are working to develop a new method for diagnosing leptospirosis, which is superior to the standard test currently used, and which will be able to detect the disease in its initial phase. In a study recently published in the journal Tropical Medicine and Infectious Disease, the strategy managed to detect the disease in more than 70% of patients who had obtained false-negative results in the first days of symptoms. According to Butantan, the new diagnosis showed 99% specificity and did not cross-react with other infectious diseases, such as dengue, malaria, HIV and Chagas disease.

In cases of dengue fever, many will be asymptomatic or mild. There is no specific antiviral to combat the virus and treatment basically consists of hydration, rest and use of medication to control fever and pain. The patient can use paracetamol or dipyrone (when there is no contraindication for use).

X-ray of diseases in Brazil

In 2023, the country recorded 3,338 confirmed cases of leptospirosis, with 281 deaths, according to the Ministry of Health. This year, considering only the first four months, 743 cases of the disease and 72 deaths were confirmed – numbers recorded up to April 14, i.e. , without considering the cases in Rio Grande do Sul. Dengue is also a national problem: the federal government has already recorded more than 5 million cases and more than 3 thousand deaths from the disease.

The State Department of Health of Rio Grande do Sul reported the registration of 3,030 cases of leptospirosis until June 3rd. Of these, 206 tested positive for the disease. Eight deaths have been confirmed and 12 are awaiting the results of confirmatory tests. The state also reported 231,497 cases of dengue, of which 146,772 were confirmed and 27,037 were still under investigation. In total, 205 people died from the disease.

After a catastrophic climate event like the one that hit Rio Grande do Sul, the population may be faced with environmental imbalances that favor the spread of infectious diseases and, therefore, it is necessary to pay attention to prevention measures. “In cases of dengue fever, the pockets of stagnant water that will emerge with the progressive drop in water levels will result in a moment to pay attention to the possible increase in cases, despite the low temperatures being unfavorable to the mosquito cycle. Remembering that contaminated mosquito eggs can remain in the environment for long periods, hatching when favorable conditions arise”, explains the infectious disease specialist at Einstein.

To prevent leptospirosis, the specialist highlights the importance of using waterproof materials (such as boots and gloves) when coming into contact with flood water, mud and environments that have been flooded. “It is also important to pay attention to hand and environmental hygiene, drink only drinking water, store food properly and maintain rodent control,” she adds. There are no vaccines for humans in Brazil.

In places that have been invaded by rainwater, it is recommended to disinfect the environment with 2.5% sodium hypochlorite, present in bleach (one glass of bleach for a 20-liter bucket of water). Keeping food stored in well-closed containers, keeping the kitchen clean, removing leftover food or pet food before dark, keeping the land clean and avoiding debris and accumulation of objects in the backyard are practices that help to avoid the presence of rodents.

In a technical note issued at the beginning of the month, the Brazilian Society of Infectious Diseases (SBI) does not recommend chemoprophylaxis (the use of antibiotics) as a routine, prevention and public health measure for the entire population. The document recommends the prophylactic use of the medication only by people at high risk of contagion, such as rescue teams and volunteers with prolonged exposure to flood water. The note highlights that the use of antimicrobials is not 100% effective, and the person can still be contaminated.

Source: CNN Brasil

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