From the Guidelines
You are typically contagious with Influenza A for 5-7 days after symptoms begin, even if you've started oseltamivir (Tamiflu), but taking oseltamivir within 48 hours of symptom onset can reduce the contagious period by about 1-2 days. The standard oseltamivir regimen is 75 mg twice daily for 5 days for adults with normal renal function, as recommended by the CDC and AAP 1. Despite medication, you should still consider yourself contagious for at least 24 hours after your fever resolves without fever-reducing medications.
To prevent spreading the virus, it is essential to:
- Stay home from work or school during this period
- Wash hands frequently
- Cover coughs and sneezes
- Consider wearing a mask around others if you must leave home
Oseltamivir works by inhibiting viral neuraminidase, preventing new virus particles from being released from infected cells, which reduces viral shedding and shortens illness duration, but it doesn't immediately stop viral shedding completely 1.
It is crucial to note that antiviral treatment should be started as soon as possible after illness onset and should not be delayed while waiting for a definitive influenza test result because early therapy provides the best outcomes 1. Clinical judgment, based on underlying conditions, disease severity, time since symptom onset, and local influenza activity, is an important factor in treatment decisions for patients who present with influenzalike illness.
In terms of reducing the risk of complications, oseltamivir has been shown to reduce the risk of acute otitis media in children 1 to 5 years of age with laboratory-confirmed influenza 1. Additionally, a meta-analysis of 5 new RCTs that included 1598 children with laboratory-confirmed influenza showed that treatment with oseltamivir significantly reduced the duration of illness in this population by 17.6 hours (95% CI, 34.7 to 0.62 hours) 1.
Overall, while oseltamivir can help reduce the contagious period and alleviate symptoms, it is essential to take preventive measures to avoid spreading the virus to others.
From the Research
Duration of Contagiousness with FLU A while taking Oseltamivir
- The duration of contagiousness with FLU A while taking oseltamivir is not directly stated in the provided studies.
- However, studies have shown that oseltamivir can reduce the duration of viral shedding and the severity of illness when initiated within 36-48 hours of symptom onset 2, 3.
- One study found that oseltamivir reduced the duration of symptomatic illness by up to 1.5 days and the severity of illness by up to 38% compared with placebo when initiated within 36 hours of symptom onset 2.
- Another study found that oseltamivir decreased the median duration of influenza-related symptoms by approximately 1 day if initiated within 48 hours of the onset of symptoms of influenza 3.
- It is also noted that oseltamivir may increase survival when used within five days of symptom onset in influenza H1N1-infected patients who require ICU admission 4.
- A more recent study found that oseltamivir prescriptions filled on the day of diagnosis were associated with significantly decreased odds of hospitalization, while prescriptions filled within 1 to 5 days of diagnosis were associated with significantly increased odds of hospitalization 5.
Factors Affecting Contagiousness
- The effectiveness of oseltamivir in reducing contagiousness may depend on various factors, including the timing of initiation, dosage, and individual patient characteristics.
- Studies have shown that early treatment with oseltamivir is more effective in reducing the risk of hospitalization and death 5, 6.
- The use of oseltamivir in combination with other treatments, such as vaccination, may also impact contagiousness 5.