The explosion in the number of cases of oropouche fever in Brazil has drawn the attention of health organizations. According to the Ministry of Health, more than 7,600 cases of the disease have been confirmed so far throughout the country. The number is at least nine times higher than the total recorded in 2023.
Amazonas is the state with the highest number of tests detecting oropouche fever, with 3,228 suspected cases, followed by Rondônia (1,710) and Bahia (844). The number of tests with suspected oropouche in Santa Catarina (169) is noteworthy, showing how the disease is no longer restricted to tropical areas, especially the Amazon region.
Given this scenario, doctors interviewed by CNN explain how to differentiate the symptoms of oropouche fever from other arboviruses — especially dengue, chikungunya and zika.
Oropouche fever is caused by the virus Orthobunyavirus oropoucheense (Orov), transmitted to humans mainly by mosquito bites Culicoides paraensisknown as maruim or sandfly. The virus was first isolated in 1960 and since then, isolated cases and outbreaks have been reported.
As a general rule, it was known that the symptoms of oropouche are very similar to those of other arboviruses: high fever, severe headache, muscle pain, nausea and diarrhea. However, some characteristics of oropouche can help differentiate it from other diseases.
According to Ralcyon Teixeira, infectious disease specialist and director of the Medical Division of the Emílio Ribas Institute of Infectious Diseases, oropouche can present:
- intense headache that does not go away, especially in the back of the neck (in dengue fever, for example, the pain is intense in the eye region);
- return of symptoms after two to three weeks (relapse).
“Patients present with the initial symptoms of oropouche and improve after two to seven days. However, when the patient is improving, a second phase of the disease can appear,” says Andrea Almeida, an infectious disease specialist at the Hospital do Servidor Público Estadual de São Paulo.
Skin rashes or even yellowing of the skin and eyes are not common in cases of oropouche. “In dengue, a skin rash appears in 50% of cases; in oropouche, this symptom is less common, between 30% and 40%. The eyes do not usually turn yellow, as in yellow fever, and conjunctivitis is not common,” explains Teixeira.
Symptoms of oropouche fever in children and pregnant women
Children should be given extra attention, according to Andrea Almeida, especially because they do not yet know how to explain exactly what they are feeling. Therefore, it is necessary to pay attention to the signs of irritability in children and associated behaviors. “The child becomes irritable and then stops eating. This happens because the headache causes discomfort. So the child stops eating (or breastfeeding, in the case of babies),” explains the doctor.
Pregnant women present symptoms very similar to those of non-pregnant adults. What draws attention to this group, however, is the possibility of vertical transmission — that is, the transmission of the virus from the pregnant woman to the fetus.
Does Oropouche cause microcephaly?
According to Maria Paula Gomes Mourão, an infectious disease specialist and researcher at the Dr. Heitor Vieira Dourado Tropical Medicine Foundation (FMT-HVD), where she leads the research group Research Center for Arboviruses, Roboviruses and Emerging Viruses in Amazonas, the experience accumulated in cases of oropouche in the state pointed to a type of disease with self-limiting evolution and almost always without complications.
“The severe forms that we had identified, until then, were of neurological impairment, with symptoms of encephalitis or meningitis — also of short evolution and without sequelae (…) However, the oropouche virus underwent genetic modifications over time that may have given it a greater capacity to adapt to new mosquitoes, greater transmission and, perhaps, greater severity”, says the researcher.
Currently, however, studies are aimed at understanding possible consequences associated with oropouche fever, such as microcephaly. This is the case of a baby from Acre who was born with congenital anomalies and died after 47 days. “Tests carried out in the laboratories of the Evandro Chagas Institute (IEC/SVSA/MS), in Belém, indicated the existence of genetic material from the virus in different tissues of the baby who was born with microcephaly, joint malformations and other congenital anomalies”, informs the Ministry of Health in a press release. The case is still being investigated to confirm the relationship between oropouche and the anomalies.
“Everything indicates that this virus can be transmitted vertically and cause harm to fetuses, as is the case with the Zika virus. It may have tropism for neural cells, but this still needs to be confirmed,” says Ester Sabino, a full professor in the Department of Pathology at the University of São Paulo’s School of Medicine (FMUSP) and coordinator of the Medical Parasitology Laboratory. The researcher is one of the authors of a preliminary international study that indicates the existence of a possible new variant of the oropouche virus.
How is oropouche diagnosed?
The diagnosis of oropouche is not made solely with the patient’s symptoms. “It is a diagnosis of exclusion”, says Andrea Almeida, an infectious disease specialist at the São Paulo State Public Servants Hospital.
The doctors interviewed by CNN as well as the Ministry of Health, indicate that symptoms can help guide the diagnosis, but their conclusion is made based on the joint analysis of the patient’s symptoms, laboratory tests (available in the SUS and private laboratories) and the epidemiological context — if the person lives or has been to a place with an outbreak of the disease, for example.
Treatment, vaccine and prevention
Yet There is no specific treatment for oropouche, nor is there a vaccine. Patients should rest, stay hydrated and take medications to relieve symptoms, such as antipyretics. As it is not yet known whether the virus can cause hemorrhagic symptoms, as in dengue fever, it is recommended not to use medications such as ibuprofen, acetylsalicylic acid, diclofenac, sodium salicylate, methylsalicylate and corticosteroids, which can facilitate hemorrhages.
With no vaccine available to prevent infection, the main prevention methods are:
- If possible, avoid areas where there are a lot of mosquitoes;
- Wear clothes that cover most of your body;
- Use mosquito repellents on exposed areas of skin;
- Remove potential mosquito breeding sites, such as standing water in tires, gutters and plant pots, and keep swimming pools and water tanks clean and covered.
The Ministry of Health warns that, in cases of suspicious symptoms, it is recommended to seek medical help immediately and inform about your potential exposure to the disease.
