Primary EBV infection is usually asymptomatic and may progress to benign lymphoproliferative disease called infectious mononucleosis (IM), especially in late childhood or early adulthood in developing countries 4.
Infectious mononucleosis is characterized by significant clinical polymorphisms in which factors such as age, immune status and comorbidities have been described as parameters in clinical evolution from asymptomatic infections to more severe conditions evidenced by acute complications, such as multiple organ failure, disseminated intravascular coagulation, ulcer/perforation of digestive tract, coronary artery aneurysm, lymphomas and lymphohistiocytes and EBV-associated hemophagocytosis 19, 20.
Mendoza et al. (2008) confirmed that EBV infection has an incubation period ranging from 4–6 weeks with prodromal symptoms of asthenia, anorexia, headache and chills, which often precede the signs and symptoms of mononucleosis: fever (that can reach 39–40° C) accompanied by pharyngotonsillitis and lymphadenopathy 21, 22, 23. In agreement, in our study, fever was the clinical finding in 65.8% (50/76), cervical lymphadenomegaly in 60.5% (46/76), pharyngitis in 19.7% (15/76), arthralgia in 17.0% (13/76), and headache in 9.2% (7/76) of the 76 patients analyzed.
Regarding the type of EBV infection, there are two different types of EBV 24. EBV types are related to variation in the EBNA2 and EBNA3 gene sequences, commonly known as types 1 and 2 17, 25.
Studies conducted in other countries have demonstrated the predominance of EBV1 infection in China with rates of 76.3%, Argentina in 75.9%, Sweden in 67% and Hong Kong 57% 26, 27, 28, 29.
Our findings revealed that EBV1 was frequent in 71.1% (54/76) of cases of infectious mononucleosis from the metropolitan area of Belém, Brazil. A total of 68 samples of Chinese individuals were studied with the aim of identifying circulating types according to the EBNA 3C gene by PCR. In total, 76.3% (45/59) of samples were EBV–1, 20.3% (12/59) were EBV–2, and 3.4% (2/59) EBV–1 and EBV–2 (coinfected), and 13.2% (9/68) of the samples did not amplify.
A study conducted by Deng et al. (2014) with samples of 209 Japanese patients obtained the following results: 146/209 (69.9%) samples had EBV, 107/146 (73.3%) were EBV- 1, 27/146 (18.5%) were EBV–2 and 12/146 (8.2%) were coinfected (EBV–1 and EBV–2), and 63/209 (30.1%) did not amplify the EBNA3C gene 30.
A study conducted in Qatar revealed similar frequencies with a predominance of EBV1 (72.5%, 37/51) compared to genotype 2 (3.5%), and mixed infections were detected in 4% of the samples 31. The determination of the types of EBV in the present study made it possible to distinguish the molecular epidemiology and circulation of these viral agents.
The most clinically relevant transferases are aminotransferase (aspartate aminotransferase - AST, alanine aminotransferase - ALT and gamma-glutamyl transferase - GGT), which express the main indexes of liver function 32, where small changes may occur in normal individuals (less than twice the reference value). In patients with infectious mononucleosis caused by EBV, values up to 5 to 10 times higher than the reference values have been reported and may even progress to fulminant hepatitis, which is not present with bilirubin abnormalities 33, 34,.
Ninety-five patients with infectious mononucleosis and 95 healthy controls were analyzed for AST, ALT and GGT; alterations were elevated in patients with infectious mononucleosis compared to the controls 34.
When compared to the EBV types (EBV1, EBV2 and EBV1/2), our results were statistically significantly correlated with the age group and AST and ALT values (p <0.005). Similar data were cited by Zhang et al. (2018), who reported that ALT, AST and GGT levels were significantly increased in cases of infectious mononucleosis compared to controls, indicating that transferase levels can be used to diagnose and treat as a risk alert for the infection caused by MI34.