Influenza

Influenza -- Is it a cold, flu or Pertussis?

The Myth of the "Stomach Flu”

Many people use the term "stomach flu” to describe illnesses with nausea, vomiting, or diarrhea. These symptoms can be caused by many different viruses, bacteria, or even parasites. The "flu" is a term that generally refers to influenza. While vomiting, diarrhea, and being nauseous or “sick to your stomach” can sometimes be related to the flu — particularly in children — these problems are rarely the main symptoms of influenza. The flu is a respiratory disease and not a stomach or intestinal disease.

Is it a Cold, Flu or Pertussis?

Colds, flu and Pertussis are highly contagious and, in the initial stages, might seem alike. Check the following table for a comparison of the symptoms for each illness.

Rapid Reference: Flu versus Cold versus Pertussis

(source: City of Milwaukee Health Department)

Symptom

Influenza ("Flu")

Cold (Viral URI)

Pertussis

Fever

Usually present & high (102-104°F or 39-40°C); typically lasts 3-4 days

Uncommon

Uncommon If present, typically low-grade

Headache

Very common

Uncommon

Aches and pains, muscle aches, chest discomfort

Common, Often severe

Slight to Moderate

Uncommon

Fatigue and weakness

Moderate - severe; can last up to 14-21 days

Mild

Mild to moderate

Extreme exhaustion

Very common early in illness

Extremely Rare

Rare

Stuffy or runny nose

Sometimes

Common

Common, early in the disease

Sneezing

Sometimes

Common

Common, early in the disease

Sore throat

Sometimes

Common

Uncommon

C
O
U
G
H

Character

Non-productive ("dry") cough is typical; nocturnal cough rare

Hacking cough, often productive; nocturnal cough rare; usually responds to cough medications

Variable character; fits / paroxysms and nocturnal cough are common; generally not responsive to cough medications

Severity

Moderate

Mild to Moderate

Variable; can be mild in adults and very severe in infants and young children

Duration

Typically 3-7 days; occasionally to 14 days

Typically 3-7 days

Persistent cough, almost always >1week, usually 2-6 weeks, sometimes 10+ weeks

Paroxysms

Uncommon

Rare

Common

Infectious Period

1-2 d before symptom onset to 5-10 days after

Variable; typically 4-7 days after symptom onset; can be longer

From start of catarrhal phase (before cough) to 21 days after cough onset*

*or until taking 5 days of appropriate anti-pertussis antibiotics, or until a nasopharyngeal pertussis PCR is negative, whichever occurs first

Last Revised: October 19, 2007