Study Highlights Increasing Risk of Vertical Transmission in Oropouche Disease Cases

The Pan American Health Organization (PAHO) recently warned its members about the risks of Oropouche disease and the State Health Department confirmed the first cases, which have been increasing in the country, in the state of São Paulo. Now, suspicions of intrauterine transmission have also been raised. “Six cases of vertical transmission (from mother to child) of Oropouche fever infection are under investigation. There are three cases in Pernambuco, one in Bahia and two in Acre. Two cases resulted in fetal death, there was one spontaneous abortion and three cases presented congenital anomalies, such as microcephaly,” according to the Ministry of Health.

However, it is still too early to definitively state a cause-and-effect relationship, that is, that miscarriages and anomalies are caused by Oropouche. Ester Sabino, director of the Institute of Tropical Medicine at the University of São Paulo School of Medicine, comments on the disease and the hypothesis that it is transmitted vertically, explaining the changes that have occurred and what needs to be done.

Changes in the Oropouche virus

Belonging to the arbovirus group, like dengue, chikungunya and zika, Oropouche arrived in Brazil in the 1960s. Despite a few episodes, it did not cause great concern. Now, according to PAHO, there are almost 7,700 confirmed cases of Oropouche in the Americas this year, of which 90% were in Brazil. Concern is growing about its potential to become an epidemic, and also because it has already caused two deaths in adults and is suspected of vertical transmission.

This scenario is at odds with the history of the virus, which has always remained on the sidelines of major diseases. Ester Sabino explains that this is due to changes in the viral structure, essentially creating a ‘new Oropouche’: “It has segments and so can recombine with others that are in nature.” The professor explains that these changes caused the current epidemic. “It is almost as if it were a new virus.”

When the old virus combines with new segments of other viruses, the result is an unpredictable disease. She compares the situation to the Influenza flu, which went through a similar process. Different “pieces” of viruses came together, giving them new characteristics and generating unprecedented effects. This would explain the current outbreak and also the vertical transmission, which is only now being investigated, despite the Oropouche virus having been in Brazil for more than half a century.

Vertical transmission

Other viruses in the same group as Oropouche are capable of mother-to-child transmission, and the same may be happening now. Zika, for example, is part of this group and caused a health crisis in 2015 because it caused many cases of microcephaly. However, despite PAHO’s suspicions, much research is still needed. The Ministry of Health itself says: “Analyses are being carried out by state health departments and specialists, with the support of the Ministry of Health, to conclude whether there is a relationship between Oropouche fever and cases of malformation or miscarriage.”

According to Ester, the scenario indicates that there is probably a relationship between the disease and cases of miscarriages and microcephaly, and that “we are moving towards determining this”, but that this will not be the end of the research. Much more than defining whether or not it is the cause, it is necessary to understand the frequency, the means and several other variables: “This does not mean that a person who was infected with Oropouche and is pregnant will have problems with the fetus. It could be something that is rare, very frequent… this next step is very important”.

There are also other types of vertical transmission, such as through natural childbirth and breastfeeding, but this varies from case to case. What needs to be done now is to study the reformulated virus and how it acts. She explains that there is no general rule for diseases and that each one acts in a different way. For example, there are diseases in which the fetus is susceptible to health complications, but the newborn is not – that is, to assume any effect, research is needed to determine it concretely.

Prevention

Comparing the situation with the Zika virus, Ester Sabino says that we have made significant progress in combating epidemics. If in 2015 intensive actions to combat the disease only took place when the epidemic was almost over, now science is acting more immediately and can also demonstrate “its full potential”.

But while little is known about this new virus, the recommendations for prevention are the same as for dengue fever: “Use insect repellent, wear long pants and sleeves – anything that prevents [people] from being bitten.” It is also worth adding the use of protective screens on windows and doors, especially in endemic areas. Pregnant women need to be extra careful to avoid any risk of affecting the fetus.

Symptoms to watch out for include “sudden onset of fever, headache, joint stiffness, body aches, and in some cases, photophobia, diplopia (double vision), persistent nausea and vomiting. Symptoms may last five to seven days. Rarely, severe cases may include aseptic meningitis” (Pan American Health Organization) .