How many days after a tick bite should blood be drawn for encephalitis and borreliosis testing?

Understanding Tick-Borne Diseases

Encephalitis and Borreliosis: A Brief Overview

What is Tick-Borne Encephalitis (TBE)?

Tick‑borne encephalitis (TBE) is a viral infection of the central nervous system transmitted by the bite of infected Ixodes ticks. The causative agent, TBE virus, belongs to the Flaviviridae family and circulates in forested regions of Europe and northern Asia where tick populations thrive.

Incidence peaks during the warm months when tick activity is highest. Humans acquire the virus through skin penetration during a tick bite; the risk increases for outdoor workers, hikers, and residents of endemic areas.

The incubation period ranges from 4 to 28 days, most often 7–14 days. Early symptoms resemble a nonspecific febrile illness (headache, malaise, fever). Approximately one third of patients progress to neurological involvement, presenting as meningitis, encephalitis, or meningo‑encephalitis with altered consciousness, focal deficits, or seizures.

Diagnostic confirmation relies on serological testing for TBE‑specific antibodies. Blood samples collected 7–14 days after the tick encounter usually contain detectable IgM, while IgG appears later and indicates past exposure. Polymerase chain reaction is useful only during the brief viremic phase, which precedes antibody formation.

Prevention centers on vaccination, which provides long‑lasting immunity when administered according to the recommended schedule. Personal protective measures—prompt removal of attached ticks, use of repellents, and wearing protective clothing—reduce the likelihood of infection.

What is Lyme Disease (Borreliosis)?

Lyme disease, also known as borreliosis, is a multisystem infection caused primarily by the spirochete Borrelia burgdorferi in North America and by several related Borrelia species in Europe and Asia. The pathogen is transmitted to humans through the bite of infected ixodid ticks, most commonly the black‑legged (deer) tick (Ixodes scapularis) in the United States and the castor‑bean tick (Ixodes ricinus) in Europe.

The clinical course progresses through distinct stages:

Early localized infection (days to weeks): Erythema migrans, a expanding erythematous rash often with central clearing, appears at the bite site. Accompanying symptoms may include fever, headache, fatigue, and myalgias.
Early disseminated infection (weeks to months): Multiple erythema migrans lesions, cranial neuropathies (e.g., facial palsy), carditis, and migratory musculoskeletal pain may develop.
Late disseminated infection (months to years): Chronic arthritis, particularly of large joints, and neuroborreliosis manifesting as peripheral neuropathy, encephalopathy, or meningitis.

Laboratory confirmation relies on serologic testing. The standard algorithm combines an initial enzyme‑linked immunosorbent assay (ELISA) to detect IgM and IgG antibodies, followed by a Western blot for confirmation. Molecular methods such as PCR are reserved for synovial fluid or cerebrospinal fluid when serology is inconclusive. Timing of specimen collection influences sensitivity: antibodies typically become detectable 2–4 weeks after exposure, while direct detection methods are most effective during early dissemination.

Effective treatment requires antibiotics targeting spirochetal organisms. Doxycycline is first‑line for most adult patients with early disease; amoxicillin or cefuroxime axetil are alternatives for children and pregnant women. Intravenous ceftriaxone is recommended for severe neurological or cardiac involvement. Early initiation of therapy usually prevents progression to later stages and reduces the risk of persistent symptoms.

Epidemiologically, Lyme disease is the most common vector‑borne illness in the United States and Europe, with incidence peaks in late spring and summer when nymphal ticks are most active. Prevention strategies include personal protective measures (e.g., repellents, tick checks) and habitat management to reduce tick exposure.

Transmission Mechanisms of Tick-Borne Pathogens

Tick-borne pathogens reach the vertebrate host primarily through the salivary secretions released during blood feeding. The rapid exchange of saliva and blood creates a direct conduit for spirochetes, viruses, and protozoa. Pathogens such as Borrelia burgdorferi and tick-borne encephalitis virus exploit this route to establish infection within minutes of attachment.

Additional transmission routes include:

Co‑feeding: Uninfected ticks acquire pathogens from neighboring infected ticks feeding on the same host, without systemic infection of the host.
Transstadial passage: Microorganisms persist through the tick’s developmental stages (larva → nymph → adult), maintaining infectivity across molts.
Transovarial transfer: Certain viruses, notably the tick-borne encephalitis virus, are passed from adult females to their offspring, enabling infected larvae to emerge already infectious.

The timing of serological testing reflects these mechanisms. After a bite, the host’s immune response to Borrelia typically becomes detectable within 2–3 weeks, whereas antibodies against the encephalitis virus appear after 7–14 days. Consequently, blood samples drawn earlier than this window often yield false‑negative results. Clinical protocols therefore recommend an initial draw at least 14 days post‑exposure, followed by a second specimen 2–4 weeks later to capture seroconversion for both agents.

Factors Influencing Testing Timing

Incubation Periods of TBE and Lyme Disease

The incubation period determines when serological markers become detectable.

For tick‑borne encephalitis (TBE), the interval between the bite and symptom onset typically ranges from 4 to 28 days, with most cases emerging between days 7 and 14. IgM antibodies appear around day 7, reach peak levels by days 14‑21, and remain elevated for several weeks. Consequently, a blood sample collected after day 10 and no later than day 21 provides reliable results for TBE testing.

For Lyme disease (borreliosis), the incubation period for the early localized stage spans 3 to 30 days, median 7‑14 days. Specific IgM antibodies usually become measurable 2 to 4 weeks post‑exposure, while IgG seroconversion follows shortly thereafter. To ensure detectable antibody levels, blood should be drawn no earlier than day 21 and preferably by day 30 after the bite.

Recommended sampling windows

TBE: day 10 – day 21 post‑bite
Lyme disease: day 21 – day 30 post‑bite

Sampling within these periods aligns with the expected appearance of diagnostic antibodies, maximizing test sensitivity.

TBE Incubation Period

The incubation period for tick‑borne encephalitis (TBE) typically ranges from 7 to 14 days, with occasional cases extending to 28 days. During this interval the virus replicates in the skin and migrates to the central nervous system, after which specific antibodies appear in the serum.

Serological testing for TBE becomes reliable when IgM antibodies are detectable, usually 5–7 days after symptom onset or 10–14 days after the bite. To obtain a definitive result, draw the first blood sample no earlier than 10 days post‑exposure. A second sample collected 2–3 weeks later confirms seroconversion and distinguishes recent infection from past exposure.

For Lyme disease (borreliosis), the antibody response is slower. Initial IgM antibodies may be present 2–4 weeks after the bite, while IgG antibodies often appear after 4–6 weeks. Consequently, the earliest useful blood draw for Lyme serology is 14 days post‑bite, with a follow‑up sample at 4–6 weeks to capture the full antibody profile.

Practical timing for combined testing

First blood draw: ≥ 10 days after tick bite (covers early TBE IgM detection).
Second blood draw: ≥ 21 days after bite (confirms TBE seroconversion and begins Lyme IgM detection).
Third blood draw (if Lyme disease suspected): ≥ 28–42 days after bite (captures Lyme IgG response).

Adhering to these intervals maximizes diagnostic sensitivity for both encephalitis and borreliosis.

Lyme Disease Incubation Period

The incubation period for Lyme disease typically ranges from three to thirty days before the characteristic skin lesion appears; neurological manifestations such as meningitis or encephalitis may develop weeks to several months after the initial bite. Early infection often produces no detectable antibodies, while the immune response capable of generating IgM and later IgG antibodies emerges around the second to fourth week post‑exposure.

Serologic testing for Borrelia burgdorferi becomes reliable after this two‑to‑four‑week window. Tests performed earlier frequently yield false‑negative results because antibody concentrations are below detection thresholds. For patients presenting with central nervous system symptoms, cerebrospinal fluid analysis can supplement serum testing, but blood samples remain essential for confirming systemic infection.

Practical guidance: obtain a blood specimen for encephalitis and Lyme disease evaluation no sooner than fourteen days after the tick bite. If neurological signs appear earlier, collect an initial sample for PCR or culture, then repeat serology after the three‑week mark to capture the developing antibody response.

Types of Diagnostic Tests

After a tick bite, laboratory confirmation of tick‑borne encephalitis and Lyme disease relies on distinct assays that become reliable at specific intervals post‑exposure.

Serologic testing is the primary tool. Enzyme‑linked immunosorbent assay (ELISA) detects IgM and IgG antibodies. For encephalitis, IgM appears roughly 7–10 days after infection, while IgG rises after 2–3 weeks. In Lyme disease, antibodies usually become detectable 2–3 weeks post‑bite; a second sample taken 2–4 weeks later confirms seroconversion.

Polymerase chain reaction (PCR) amplifies pathogen DNA directly from blood, cerebrospinal fluid, or skin biopsy. PCR is most sensitive during the early viremic phase, typically within the first week after the bite, before antibodies are produced.

Cerebrospinal fluid (CSF) analysis supports encephalitis diagnosis. Elevated leukocyte count, protein, and the presence of intrathecal IgM or IgG synthesis are informative. CSF should be obtained when neurological symptoms develop, generally 5–10 days after exposure.

Western blot or immunoblot serves as a confirmatory assay for Lyme disease after a positive ELISA. It distinguishes specific Borrelia protein bands and is interpreted on a convalescent sample collected at least 4 weeks post‑exposure.

Culture is rarely used because Borrelia grows slowly and requires specialized media; it is reserved for research settings.

Summary of test timing

PCR: within 0–7 days post‑bite (early detection).
IgM serology (ELISA): 7–10 days for encephalitis, 14–21 days for Lyme disease.
IgG serology (ELISA): ≥21 days for both agents; repeat at 4–6 weeks for confirmation.
CSF analysis: when neurological signs appear, usually 5–10 days after exposure.
Western blot: ≥28 days for Lyme disease confirmation.

Choosing the appropriate assay and sampling interval maximizes diagnostic yield while minimizing false‑negative results.

Serological Tests (Antibody Detection)

Serological testing for tick‑borne encephalitis (TBE) and Lyme disease relies on detection of specific IgM and IgG antibodies. Antibody levels become measurable only after the host’s immune response is established, which dictates the timing of blood collection.

The first serum sample should be obtained no earlier than 7 – 14 days after the bite or the onset of symptoms. At this point IgM antibodies against TBE virus and Borrelia burgdorferi are usually detectable, while IgG may still be low. A second sample taken 2 – 4 weeks later confirms seroconversion and allows quantification of IgG, which is essential for definitive diagnosis of both infections.

Key timing points:

Initial draw: 7–14 days post‑exposure (or symptom onset). Detects early IgM response.
Follow‑up draw: 14–28 days after the first sample. Confirms rise in IgG and validates initial result.

Testing earlier than 7 days carries a high risk of false‑negative results because antibody titers are often below detection thresholds. In such early presentations, molecular methods (PCR) are preferred, but serology remains the standard for definitive diagnosis after the immune response has matured.

PCR Testing (Direct Pathogen Detection)

Polymerase‑chain‑reaction (PCR) provides direct detection of pathogen nucleic acids in clinical specimens. After a tick attachment, the optimal interval for obtaining a blood sample depends on the biology of the targeted agent.

Tick‑borne encephalitis virus (TBEV) produces a brief period of viremia. Detectable viral RNA in serum peaks between days 3 and 10 post‑bite. Sampling within this window yields the highest probability of a positive PCR result. Testing after day 10 rarely detects virus in blood, although cerebrospinal fluid may remain PCR‑positive for a few additional days.
Borrelia burgdorferi, the causative agent of Lyme disease, circulates at low levels in peripheral blood. PCR sensitivity in serum is low throughout the early phase. Positive results are most likely after the spirochetes have disseminated, typically 2–4 weeks after exposure, and are more reliable in skin biopsies or cerebrospinal fluid when neuroborreliosis is suspected. Consequently, blood PCR is not the preferred diagnostic tool for early Lyme disease; serology after the second week is standard.

In practice, clinicians should draw blood for TBEV PCR between the third and tenth day following a tick bite, and consider PCR on alternative specimens (e.g., CSF) if neurological symptoms develop later. For Lyme disease, blood PCR is generally reserved for later stages or specific clinical scenarios; otherwise, serological testing after the second week remains the primary approach.

Immune Response Dynamics

The timing of serologic sampling after a tick exposure must align with the kinetics of the host’s antibody response to the two principal pathogens.

Tick‑borne encephalitis virus (TBEV):
• IgM becomes detectable 5–7 days post‑exposure, reaches maximal concentration around 2–3 weeks.
• IgG appears after 10–14 days, continues to rise for several weeks.
• For reliable serology, draw blood no earlier than 10 days, preferably 14–21 days.
Borrelia burgdorferi (Lyme disease):
• IgM antibodies emerge 2–4 weeks after the bite, peak near the fourth week.
• IgG antibodies develop 4–6 weeks post‑exposure, stabilize thereafter.
• Optimal sampling for early detection occurs at 3–4 weeks; confirmatory testing is most accurate after 5 weeks.

Early in infection, nucleic‑acid amplification tests may identify TBEV RNA within the first week, but they lose sensitivity as viremia wanes. For Lyme disease, direct detection of spirochetes from blood is unreliable beyond the initial days, making antibody assays the standard diagnostic tool.

Thus, the immune response dictates distinct windows for blood collection: roughly two weeks for viral encephalitis serology and three to five weeks for bacterial borreliosis serology. Aligning sampling with these intervals maximizes diagnostic yield.

Early Immune Response to TBE

After a tick bite that transmits tick‑borne encephalitis virus, the host’s immune system reacts within hours. Viral particles are captured by dermal dendritic cells and macrophages, which produce type I interferons and pro‑inflammatory cytokines (IL‑6, TNF‑α, IL‑1β). Natural‑killer cells are recruited to the bite site, contributing to early viral control.

Within the first 48 hours, viral RNA may be detectable in blood. By day 3–4, the innate response peaks, and antigen‑presenting cells migrate to regional lymph nodes, initiating the adaptive phase. Specific IgM antibodies appear typically between days 5 and 7, while IgG seroconversion occurs after day 10. The rise of IgM provides the earliest serological marker for TBE infection.

For diagnostic sampling, the following timeline is critical:

Days 1–2: PCR for viral RNA yields the highest sensitivity; serology is usually negative.
Days 5–7: IgM ELISA becomes reliable; a single sample may confirm recent infection.
Days 10 onward: IgG detection supports diagnosis and indicates progression toward immunity.

Early testing should therefore target the window of detectable viremia for molecular assays, followed by IgM measurement as the adaptive response emerges. Aligning blood collection with these intervals maximizes diagnostic yield for both encephalitis and concurrent borreliosis evaluation.

Early Immune Response to Lyme Disease

A tick bite introduces Borrelia burgdorferi, the agent of Lyme disease, into the skin. Within hours, innate immune cells recognize pathogen‑associated molecular patterns through Toll‑like receptors, triggering rapid secretion of interleukin‑6, tumor‑necrosis factor‑α, and interferon‑γ. Neutrophils and macrophages infiltrate the bite site, phagocytosing spirochetes and releasing chemokines (CXCL1, CXCL8) that amplify cellular recruitment. Complement activation occurs simultaneously, limiting early dissemination but also contributing to local inflammation.

Adaptive immunity emerges after 7–10 days. Naïve B cells differentiate into IgM‑producing plasmablasts, detectable in peripheral blood around day 14. IgG class switching follows, reaching measurable levels by 3–4 weeks. T‑cell responses are characterized by a Th1 bias, with interferon‑γ‑producing CD4⁺ cells supporting macrophage activation. The early serologic window—when antibodies are still low—reduces the sensitivity of standard ELISA and Western blot assays.

Testing for central nervous system involvement and systemic borreliosis therefore requires timing that aligns with immune kinetics:

PCR of blood or cerebrospinal fluid: viable from the first day after exposure; optimal within 7–10 days when spirochetemia peaks.
IgM serology: reliable beginning around day 14; repeat at day 21 if initial result is negative and clinical suspicion persists.
IgG serology: most sensitive after day 28; useful for confirming later-stage infection.

Drawing blood for encephalitis evaluation should occur no earlier than the first week post‑bite to capture potential PCR positivity, while serologic specimens are best collected between two and four weeks to ensure detectable antibody levels.

Recommended Blood Draw Timelines

Testing for Tick-Borne Encephalitis (TBE)

Initial Blood Draw Recommendations for TBE

The first serum sample for tick‑borne encephalitis (TBE) should be collected as early as possible after the bite, preferably within the first 7 days. Early collection captures the initial immune response and provides a baseline for later comparison. If the bite date is uncertain, draw the specimen at the time of presentation and note the estimated exposure interval.

A second sample is essential for diagnostic confirmation. Collect it 14–21 days post‑exposure, when IgM antibodies typically become detectable. For patients with delayed symptom onset, a third draw 28 days after the bite can verify seroconversion and differentiate recent infection from past exposure.

Key points for the initial draw:

Aim for ≤ 7 days after the tick bite.
Use serum or plasma; avoid anticoagulants that interfere with ELISA.
Record exact or estimated bite date, site of attachment, and any prophylactic measures.
Pair the sample with a questionnaire on symptoms and recent vaccinations, as prior TBE immunization can affect antibody patterns.

Timing aligns with the pathogen’s incubation period (5–15 days) and maximizes the likelihood of detecting early serologic markers, facilitating prompt clinical decisions and appropriate follow‑up testing.

Follow-up Testing for TBE

Blood drawn for tick‑borne encephalitis (TBE) follow‑up should be timed to capture the serologic response. The first specimen is taken as soon as possible after the bite if symptoms appear; a second specimen is required during the convalescent phase to confirm seroconversion.

Initial sample: day 0‑3 after the bite (or at symptom onset).
Convalescent sample: day 10‑14 post‑exposure.

If the first test is negative and clinical suspicion remains, a third sample can be collected at day 21‑28 to detect late IgG rise.

Early PCR testing is limited to the first 7 days and is not routinely reliable for TBE; serology remains the standard. IgM antibodies usually appear by day 7‑10, while IgG becomes detectable after day 14. Therefore, drawing blood between the 10th and 14th day provides the most informative result for confirming infection.

Interpreting TBE Test Results

After a tick bite, serologic testing for tick‑borne encephalitis (TBE) must be timed to capture the immune response. An initial sample taken too early often yields negative results because antibodies have not yet reached detectable levels.

Interpretation of TBE laboratory findings relies on the pattern of immunoglobulins:

IgM present, IgG absent – indicates recent infection; sample likely taken within the first two weeks after symptom onset.
Both IgM and IgG present – suggests active infection progressing toward convalescence; IgG rise confirms immune response.
IgM absent, IgG present – points to past exposure or vaccination; no current disease activity.
Both IgM and IgG absent – does not rule out early infection; a second sample should be drawn after 14‑21 days from the bite to allow seroconversion.

A single negative result obtained within the first week after exposure should be followed by a repeat test. Rising titers between paired samples confirm recent infection, while stable low titers indicate prior immunity. Cross‑reactivity with other flaviviruses may produce weakly positive results; confirmatory neutralization assays are recommended when the clinical picture is ambiguous.

Testing for Lyme Disease (Borreliosis)

Initial Blood Draw Recommendations for Lyme Disease

Initial blood draw for suspected Lyme disease should be timed to maximize serologic sensitivity while allowing early detection of possible central‑nervous‑system involvement. The following points summarize current recommendations:

Perform the first venipuncture at least 14 days after the bite if the patient is asymptomatic. Antibody production against Borrelia burgdorferi typically becomes detectable during this window.
If systemic symptoms (fever, headache, arthralgia) or a rash appear before the 14‑day mark, obtain a sample immediately. Early testing can identify acute infection through polymerase chain reaction or IgM responses, though false‑negative results remain possible.
In cases with neurological signs suggestive of encephalitis, draw blood concurrently with cerebrospinal fluid collection, regardless of elapsed time, to assess both serology and inflammatory markers.
Schedule a second draw 4–6 weeks after the initial sample to confirm seroconversion or to evaluate rising titers. This follow‑up improves diagnostic certainty and guides treatment decisions.

These intervals balance the need for prompt clinical action with the kinetics of antibody development, ensuring reliable detection of Lyme disease and related neuroinvasive complications.

Follow-up Testing for Lyme Disease

Follow‑up testing for Lyme disease after a tick bite must consider the pathogen’s replication cycle and the immune response required for detectable antibodies. Blood specimens drawn too early often yield false‑negative results for both Borrelia burgdorferi and tick‑borne encephalitis virus.

For serologic detection of Borrelia antibodies, the first reliable sample is usually obtained 10–14 days post‑exposure; a second specimen collected 3–4 weeks after the bite improves diagnostic accuracy.
For tick‑borne encephalitis, IgM antibodies typically appear 7–10 days after infection, with IgG seroconversion occurring 2–3 weeks later; a confirmatory sample taken 14–21 days post‑bite is recommended.

Interpretation of results should incorporate clinical presentation, regional prevalence, and any prior antibiotic therapy. Repeating serology after the recommended interval resolves ambiguous initial findings and guides treatment decisions.

Interpreting Lyme Disease Test Results

When blood is collected after a tick bite, the interval before sampling influences the reliability of serologic markers for both central‑nervous‑system inflammation and Borrelia infection. Interpreting the results requires awareness of the antibody kinetics, assay limitations, and clinical context.

Early‑stage infection may produce a negative IgM/IgG panel because antibodies typically appear 2–3 weeks after exposure. A specimen taken too soon can yield a false‑negative result, prompting repeat testing after the recommended waiting period. Conversely, a sample drawn several weeks later may show persistent IgG positivity that does not distinguish active disease from past exposure; clinical correlation becomes essential.

Key points for result interpretation:

IgM detection: Indicates recent exposure; reliable only if the sample is collected at least 2 weeks post‑bite. Presence without compatible symptoms may represent a nonspecific response.
IgG detection: Reflects established infection; remains elevated for months to years. Positive IgG alone cannot confirm current disease without supporting signs.
Western blot confirmation: Required when ELISA yields a positive or equivocal result. Specific band patterns (e.g., OspC, VlsE) increase diagnostic confidence.
Cerebrospinal fluid (CSF) analysis: For suspected encephalitis, intrathecal antibody production or pleocytosis adds weight to the diagnosis. Blood results should be interpreted alongside CSF findings.
Repeat testing: Recommended if initial serology is negative but clinical suspicion persists, especially when the first draw occurred before the antibody window closes.

Accurate interpretation integrates the timing of specimen collection, the type of antibodies detected, confirmatory testing, and the patient’s neurological presentation. This approach minimizes misdiagnosis and guides appropriate antimicrobial therapy.

Special Considerations

Asymptomatic Bites

An asymptomatic tick bite occurs when a person experiences no immediate skin reaction, fever, or neurological symptoms after removal of the arthropod. Absence of symptoms does not eliminate the possibility of early infection with Borrelia burgdorferi or tick‑borne encephalitis (TBE) viruses, both of which may remain undetectable in the first days after exposure.

Serologic markers for Lyme disease typically become measurable 2–3 weeks post‑exposure, while TBE‑specific IgM antibodies appear around day 7 and reach peak levels by day 14. Testing before these intervals yields a high false‑negative rate, compromising diagnostic accuracy.

Recommended blood‑draw schedule for asymptomatic exposures

Day 7 ± 1: Collect serum for TBE IgM; results guide need for follow‑up.
Day 14 ± 2: Obtain combined TBE IgG/IgM panel and Lyme disease IgM/IgG ELISA; repeat if initial Lyme ELISA is negative.
Day 21 ± 3: Perform confirmatory Western blot for Lyme disease if ELISA remains negative but clinical suspicion persists; repeat TBE IgG if earlier results were borderline.

Testing earlier than day 7 is generally discouraged unless rapid progression of symptoms occurs. Adhering to the outlined timeline maximizes detection probability while minimizing unnecessary repeat sampling.

Multiple Tick Bites

When a patient experiences several tick exposures, the timing of serological sampling must reflect the earliest possible infection. For tick‑borne encephalitis, IgM antibodies typically become detectable 7 – 10 days after the first bite, while IgG seroconversion appears after 3 – 4 weeks. Therefore, draw an initial blood specimen at day 7‑10 to capture early IgM, and repeat at day 21‑28 to assess IgG development.

For Lyme disease, the bacterium Borrelia burgdorferi usually elicits a measurable IgM response 2 – 4 weeks post‑exposure, with IgG emerging 4 – 6 weeks later. In the context of multiple bites, obtain the first sample at least 14 days after the earliest known attachment to allow for IgM detection, and a second specimen at 30‑45 days to confirm IgG conversion.

Key points for multiple exposures:

Earliest bite determines the baseline – schedule the first draw 7‑10 days after that event for encephalitis IgM, 14 days for Lyme IgM.
Follow‑up sampling – repeat at 21‑28 days for encephalitis IgG, and at 30‑45 days for Lyme IgG.
Clinical correlation – interpret results alongside symptom onset; early neurologic signs may warrant immediate testing despite the usual window.

Adhering to this schedule maximizes diagnostic yield while accommodating the staggered nature of several tick contacts.

Immunocompromised Individuals

Immunocompromised patients often exhibit delayed antibody production after a tick exposure, which influences the timing of serologic testing for tick‑borne encephalitis and Lyme disease. Early sampling (approximately 7 days post‑exposure) may miss seroconversion in this group; therefore, clinicians should consider later collection points.

First draw: 10–14 days after the bite, when IgM antibodies for encephalitis viruses and early‑stage Borrelia may become detectable.
Second draw: 21–28 days post‑bite, to capture delayed IgG responses that are common in patients with weakened immunity.
Optional third draw: 35–42 days if initial results are negative and clinical suspicion persists, ensuring that late seroconversion is not overlooked.

Repeat testing with paired sera (acute and convalescent samples) improves diagnostic accuracy, especially when the immune response is attenuated. Adjustments to the schedule should be based on the specific immunosuppressive condition, severity of symptoms, and epidemiologic risk.