From the Guidelines
Influenza A is contagious for approximately 5 days after symptom onset in adults, although this period can be longer in immunosuppressed individuals and children, up to 10 or more days. According to the study published in the American Journal of Transplantation 1, patients with influenza are contagious to others 1 day before symptoms develop. The contagious period can vary, but adults generally remain infectious for about 5 days after symptoms appear. It's essential to note that children and people with weakened immune systems, such as solid organ transplant recipients, may be contagious for a more extended period. To reduce transmission, it's crucial to practice good hygiene, including frequent handwashing, covering coughs and sneezes, and disinfecting commonly touched surfaces.
Some key points to consider:
- Influenza A can spread through large respiratory droplets produced during coughing or sneezing, which can be directly deposited on the mucosal surfaces of people within 3 to 6 ft of the infected patient 1.
- The virus can also contaminate nearby surfaces, leading to spread when susceptible individuals touch contaminated areas and then touch mucosal surfaces on their face 1.
- Influenza A remains viable on hard nonporous surfaces for 24–48 h and may persist less than 8–12 h on porous materials such as cloth or paper 1.
- Isolation precautions, including Standard and Droplet Precautions, should be implemented for patients with influenza-like illness, and visitors with respiratory symptoms should be discouraged 1.
Overall, it's crucial to take precautions to prevent the spread of influenza A, especially in high-risk populations such as solid organ transplant recipients, by practicing good hygiene and following isolation guidelines.
From the Research
Duration of Contagiousness
- The duration of contagiousness for Flu A is not directly stated in the provided studies 2, 3, 4, 5, 6.
- However, the studies discuss the effectiveness of antiviral drugs such as zanamivir and oseltamivir in treating influenza A and B, which can indirectly relate to the duration of contagiousness.
- For example, a study found that zanamivir and oseltamivir can decrease the median duration of influenza-related symptoms by approximately 1 day if initiated within 48 hours of the onset of symptoms of influenza 2.
- Another study compared the effectiveness of zanamivir and oseltamivir for the treatment of influenza A and B, and found that zanamivir therapy is more effective than oseltamivir for the treatment of influenza B infection 3.
Treatment and Contagiousness
- The studies suggest that early treatment with antiviral drugs such as zanamivir and oseltamivir can help reduce the duration of contagiousness by shortening the duration of symptoms and reducing the viral load 2, 3, 4, 5, 6.
- A study found that inhaled zanamivir is not inferior to oral oseltamivir in preventing influenza-related hospitalization or death for patients whose conditions do not require hospitalization within 2 days 6.
- Another study reported on two critically ill patients with influenza pneumonia, where oseltamivir monotherapy did not result in clearance of the virus, but the addition of zanamivir and amantadine to the treatment led to negative PCRs on pharyngeal and/or plasma specimens after 4 and 3 days, respectively 4.