The discovery of the first indigenous case of infection by virus Mosquito usutu in Spain set off alarms in the health system. This virus, detected in a blood donor Majorca Through routine analyzes in the summer of 2024, it confirms that the agent circulates locally.
The case was validated by the National Arbovirus Reference Laboratory of the Carlos III Health Institute through molecular tests and neutralization analysis, after the initial test gave a positive result for the West Nile virus.
He Usutu virus it’s a arbovirus belonging to the Flaviviridae family. It was identified in Africa in 1959 and is named after the Usutu River, located near the site of its discovery. Originally it affects a wide variety of bird species, which act as a natural reservoir. In recent decades, The Usutu virus has spread steadily through various European countrieswhere it is linked to outbreaks in wild birds and occasionally to human infections.
Usutu virus structurally resembles West Nile viruspresents a genetic similarity of 76 to 78 percent, and both are detected with crossed techniques in blood banks.
The main transmission of the Usutu virus to humans occurs through the bite of mosquitoes of the genus Culex. The usual cycle involves infected birds: a mosquito feeds on a bird carrying the virus and then bites a person, thus incidentally transmitting the virus. According to the doctor Teresa Jimenezmedical director of Balearic Blood and Tissue Bankwho explained to EFEhumans are not the main target of this virus, but “it is possible that infections may occur, especially in areas where migratory birds circulate and there is high mosquito activity.”
Another route of contagion identified in this Spanish case is blood transfusion. If an infected but asymptomatic person donates blood, the virus can be transferred to the recipient, something highlighted in an article published in the scientific journal Transfusion.
There is no scientific evidence of direct transmission between humans, nor of contagion through physical contact, saliva or respiratory secretions.
The Usutu virus infection In humans it usually goes unnoticed: most cases are asymptomatic or present mild discomfort. Symptoms that may appear include:
- High fever
- Headaches
- General malaise
- Neurological disorders in some cases, such as meningoencephalitis
In the immunosuppressed population or in people with previous illnesses, The virus can trigger serious complications, especially neurological ones.. A relevant fact is that, after a year of follow-up, the infected Mallorcan donor did not experience symptoms or sequelae.
The first autochthonous case was identified in Majorcawhere the affected person had not left the islands in months prior to the donation. The seasonal screening protocol, implemented for the control of West Nile virusallowed us to detect the presence of Usutu during the months of maximum mosquito activity.
After the case of Mallorca, it was confirmed two additional infections in blood donors from Catalonia. None of those involved had a travel history outside their autonomous community, which demonstrates local circulation of the virus in the Iberian Peninsula.
The doctor Jimenez highlighted EFE that “this case is an emblematic example of the concept of global health”, underlining the convergence between animal, human and environmental health.
The discovery reveals the capacity of Spanish health surveillance programs to detect emerging and potentially dangerous agents for public health. It also emphasizes the importance of reinforced supervision in blood banks during seasons of mosquito activity.
The retrospective study demonstrated that tests designed to identify West Nile Virus also allow early tracking of the virus. Usutu virusthanks to the cross-reactivity observed in the laboratories of the Carlos III Health Institute.
This episode illustrates the impact of environmental changes, bird migration and the presence of vectors on the spread of viral infections on the European continent. Institutions like the Balearic Blood and Tissue Bankhe Blood and Tissue Bank of Cataloniahe National Center for Microbiology and different international entities are currently collaborating in surveillance.
Among the main actions, Spanish and European blood banks reinforced controls in periods of greatest mosquito activity. Constant epidemiological surveillance and updating of detection protocols They especially seek to protect immunosuppressed people and patients who require blood transfusions.
