From the Guidelines
People with influenza are contagious for approximately 5 days after symptom onset, although this period can be longer for immunosuppressed individuals and children, lasting up to 10 or more days. The duration of contagiousness after contracting influenza is a critical factor in preventing the spread of the disease. According to the study published in the American Journal of Transplantation 1, patients with influenza are contagious to others 1 day before symptoms develop.
Key Points to Consider
- The contagious period for adults is approximately 5 days after symptom onset 1.
- Immunocompromised individuals and children may be contagious for 10 or more days 1.
- The virus 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.
- Aerosolized respiratory secretions may 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, while it may persist less than 8–12 h on porous materials such as cloth or paper 1.
Prevention Measures
- Cough etiquette should be encouraged, and tissues and hand sanitizer should be provided to patients with symptoms of influenza-like illness 1.
- Masks should be provided to patients who are actively coughing and sneezing until they can be placed in a private room 1.
- Isolation precautions, including Standard and Droplet Precautions, should be implemented for patients requiring hospital admission for influenza-like illness 1.
- Hospital visitors with respiratory symptoms should be discouraged, and healthy visitors should be required to wear appropriate personal protective equipment when visiting infected patients 1.
From the Research
Duration of Contagiousness
The duration of contagiousness after contracting influenza (flu) is not explicitly stated in the provided studies. However, some studies provide information on the transmission of influenza and the effectiveness of interventions to prevent its spread.
- The study 2 mentions that early treatment of index patients with influenza infection and post-exposure prophylaxis in specific populations is crucial in preventing influenza transmission.
- The study 3 reports on preventive behaviors used by adults to avoid catching or spreading influenza, including staying home when sick, but does not provide information on the duration of contagiousness.
- The study 4 investigates the effectiveness of hand hygiene and use of facemasks in preventing household transmission of influenza, but does not provide information on the duration of contagiousness.
- The study 5 reviews the efficacy and safety of drugs currently available to treat influenza, but does not provide information on the duration of contagiousness.
- The study 6 assesses the effectiveness of physical interventions to interrupt or reduce the spread of acute respiratory viruses, including influenza, but does not provide information on the duration of contagiousness.
Key Findings
Some key findings from the studies include:
- Early treatment of index patients with influenza infection and post-exposure prophylaxis in specific populations is crucial in preventing influenza transmission 2.
- Hand hygiene and facemasks may prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset 4.
- There is low certainty evidence that wearing a mask may make little or no difference to the outcome of influenza-like illness compared to not wearing a mask 6.
- Hand hygiene may offer a benefit with an 11% relative reduction of respiratory illness, but with high heterogeneity 6.
Note: There are no research papers that directly answer the question of the duration of contagiousness after contracting influenza (flu). The information provided is based on the available studies, but it does not directly address the question.