From the Guidelines
White blood cell counts can remain elevated for several months after a Covid-19 infection, particularly in patients with long Covid, with some studies suggesting that symptoms can persist for more than 12 weeks after acute infection. The duration of elevated white blood cell counts following a viral infection, including Covid-19, can vary significantly depending on the severity of the infection, individual immune response, and presence of complications 1. Covid-19 can affect white blood cell counts in different ways, initially causing lymphopenia (decreased lymphocytes) while sometimes increasing neutrophils, resulting in an overall normal or slightly elevated white blood cell count.
Key Considerations
- In severe cases, white blood cell counts may become significantly elevated due to the inflammatory response.
- After Covid-19 infection, white blood cell counts generally normalize within 2-4 weeks, though some patients with long Covid may experience prolonged inflammation with mildly elevated counts for several months.
- The timeline for normalization depends on infection severity, individual immune response, and presence of complications.
Monitoring and Management
- Regular monitoring of complete blood counts is recommended for those with persistent symptoms or concerns about recovery, as prolonged elevation could indicate secondary infection or other complications requiring medical attention.
- Patients with symptoms lasting more than 12 weeks after acute Covid-19 should be referred to medical care, while those with symptoms 4 to 12 weeks after acute infection should be assessed on a case-by-case basis, according to the severity and course of symptoms 1.
From the Research
White Blood Cell Counts After Viral Infection
- White blood cell counts can remain elevated for a period of time following a viral infection, including COVID-19 2, 3.
- The duration of elevated white blood cell counts can vary depending on the severity of the infection and the individual's response to treatment 4, 5.
COVID-19 and White Blood Cell Counts
- COVID-19 can significantly affect white blood cell counts, with some patients experiencing leukopenia (low white blood cell count) or leukocytosis (high white blood cell count) 2, 3.
- The neutrophil-to-lymphocyte ratio (NLR) has been shown to be a useful marker in determining the severity of COVID-19 and the effectiveness of corticosteroid therapy 3.
- Patients with COVID-19 who have a high NLR (> 6.11) may benefit from corticosteroid therapy, while those with a low NLR (≤ 6.11) may not 3.
Duration of Elevated White Blood Cell Counts After COVID-19
- The duration of elevated white blood cell counts after COVID-19 infection can vary, but it is generally recommended to monitor white blood cell counts for several weeks after infection 4, 5.
- Some studies have shown that white blood cell counts can remain elevated for up to 2-3 months after COVID-19 infection, although this can vary depending on the individual and the severity of the infection 6.
- It is essential to note that the duration of elevated white blood cell counts can be influenced by various factors, including the severity of the infection, the effectiveness of treatment, and the individual's overall health status 2, 3, 4, 5, 6.