From the Guidelines

Influenza A is associated with a low risk of meningitis, and the correlation between the two is not strongly established.

A multicenter prospective cross-sectional study of 1,091 febrile infants aged 60 days or younger with fever evaluated during 3 consecutive influenza seasons showed a significantly decreased risk of overall severe bacterial infection (SBI) in patients testing positive for influenza, with no cases of meningitis in the influenza-positive group (0/119=0% [95% CI 0% to 2.5%]) 1.
Another study found that influenza A has been reported in association with acute necrotizing encephalopathy (ANE), a severe encephalopathy often associated with fever, but the mechanisms for causing neurological illness are still unclear 1.
The management of encephalitis guidelines by the Infectious Diseases Society of America notes that encephalitis should be distinguished from encephalopathy, and that the objective is to provide clinicians with evidence-based recommendations in the approach to patients with encephalitis 1.

The evidence suggests that influenza A is not a common cause of meningitis, and that the correlation between the two is not strongly established.
Other viral infections, such as enteroviruses and rotavirus, are more commonly associated with meningitis than influenza A.
Bacterial meningitis is a more common and serious condition than viral meningitis, and is often associated with other bacterial infections, such as pneumonia or sepsis.

Clinicians should consider influenza A as a potential cause of encephalitis or encephalopathy, but should also consider other potential causes, such as bacterial or viral infections.
The diagnosis of meningitis or encephalitis should be based on clinical presentation, laboratory tests, and imaging studies, rather than solely on the presence of influenza A.
Treatment for meningitis or encephalitis should be guided by the underlying cause, and should include antimicrobial agents, supportive care, and other therapies as needed.

From the Research

The correlation between influenza A and meningitis is supported by several studies, which suggest a potential link between the two conditions.

Influenza A has been associated with an increased risk of meningococcal disease, with one study finding that patients with meningococcal disease were more likely to show serological evidence of recent influenza A infection 2.
Influenza viruses, including influenza A, can cause viral meningitis, although enteroviruses are the most common cause of this condition 3.
There have been reported cases of meningitis associated with influenza A virus infection, including a case of Vogt-Koyanagi-Harada disease with meningitis 4.
The mechanisms underlying the association between influenza A and meningococcal disease are not fully understood, but may involve the enhancement of meningococcal adhesion to epithelial cells by influenza A virus neuraminidase 5.
There have been reports of meningococcal disease complicating influenza A(H1N1) infection, highlighting the importance of prompt detection and treatment of this co-infection 6.

Influenza A infection may increase the risk of meningococcal disease through immune suppression or a lowering of mucosal resistance to meningococcal invasion 2.
The neuraminidase of influenza A virus may play a role in facilitating meningococcal adhesion to epithelial cells 5.
Meningococcal disease can present as a complication of influenza A(H1N1) infection, and prompt treatment with antibiotics is essential 6.