Infectivity

The incubation period for influenza is one to four days. The period of infectivity depends on many factors, and has the following typical characteristics:
in adults , it lasts six days – secretion of virus usually starts one day before the appearance of clinical symptoms and lasts approximately five days;
in children, infectivity can last for up to ten days (small children can secrete virus even six days before the appearance of the first clinical symptoms of the disease);
in individuals with severely compromised resistance, secretion of virus can last ­for several weeks or months.