While COVID-19 typically presents with fever, cough, and breathing difficulties, rarer symptoms like headaches, nausea, and vomiting have emerged. A study from China indicates the virus may also target the central nervous system.
Headaches, nausea, and vomiting often signal neurological issues. Among COVID-19 patients, 8% experience headaches and 1% report nausea or vomiting. In a study published February 27, 2020, in the Journal of Medical Virology, Yan-Chao Li, a researcher at Jilin University in China, investigated whether these symptoms point to the virus attacking the central nervous system.
Coronaviruses primarily target the respiratory system, but prior research shows some can invade the central nervous system, leading to neurological disorders (neurotropism). This applies to betacoronaviruses like SARS, MERS, and COVID-19.
For instance, HEV 67N—a coronavirus in pigs and the first identified for brain invasion—shares about 91% homology with HCoV-OC43, a human common cold coronavirus.
The exact mechanism by which coronaviruses reach the central nervous system is unclear. They may travel via synapses from the cardiorespiratory system to the spinal cord, entering through mechanoreceptors and chemoreceptors in the lower respiratory tract.
Recent cases link COVID-19 to anosmia—a loss of smell, often with taste loss—which could stem from olfactory nerve damage, the first cranial nerve linking the nasal cavity to the brain's olfactory bulb. However, anosmia is common in many respiratory illnesses and isn't uniquely tied to COVID-19.
Ultimately, COVID-19's neurotropism remains speculative, as the virus has not been detected in patients' brainstems. In contrast, SARS and MERS were found there in mouse studies.
