Transmission happens when a person comes into direct contact with respiratory droplets from someone who has the disease or is a carrier of the disease.

The worst form of invasive H. influenzae disease is meningitis. Meningitis is when the coverings of the brain and spinal cord become inflamed and swollen. Signs of meningitis include fever, weakness, vomiting, and a stiff neck. Other types of H. influenzae, including Hib, can also lead to infections in various parts of the body like the lungs, blood, joints, bones, throat, and heart coverings. Symptoms will be different depending on the area of the body that is affected.

It can be difficult to determine when someone is infected with H. influenzae. This is because many people carry the bacteria without showing any symptoms. If someone does become sick after exposure, it usually happens within 10 days, but it could take up to 60 days.

A person with discharge from their nose or throat containing the organism H. influenzae can spread the infection to others. This contagious period lasts until 24 hours after they start taking appropriate medication to prevent the spread of the bacteria. If the person has developed a serious illness due to the bacteria, treatment may not clear the bacteria from the nose or throat. People exposed to the bacteria more than seven days before the infected person shows symptoms do not have a higher risk of getting sick. Those with Hib cases are most infectious in the three days before they show symptoms.

Invasive Hib disease is preventable by giving the Hib vaccine to kids 2-18 months of age. To avoid getting sick from Hib and other types of H. influenzae, it's important to keep patients isolated from others and make sure to wash hands well.

• CDC Pink Book Haemophilus influenzae Vaccine Center for Disease Control and Prevention’s (CDC) Haemophilus influenzae Vaccine Chapter within the Pink Book  
• For Healthcare Professionals Haemophilus influenzae Vaccine information for healthcare professionals on the CDC website 
• For the Public Haemophilus influenzae Vaccine information for the public FAQs on the CDC website  
• ACIP Recommendations Most recent articles and recommendations for Haemophilus influenzae vaccination from the Advisory Committee on Immunization Practices. 

Keep children with bacterial meningitis, like that caused by H. influenzae, out of school or childcare until they have written permission from a healthcare provider and until they are fever-free for 24 hours without the use of fever-suppressing medications. See rules for exclusion of sick children from school and childcare in the Texas Administrative Code, 25 Tex. Admin. Code §97.7. 

Haemophilus influenzae (all serotypes) have been steadily increasing between 2016 to 2018 from 317 to 464 cases respectively. In 2019, cases dropped to 452. Before 2016, only invasive disease caused by H. influenzae type b (Hib) was reportable. Hib disease is rare in Texas. Since 2000, there have been an average of 9 (range of 2-15) Hib cases reported each year in Texas with 5 reported in 2018 and 9 in 2019. The majority of Haemophilus influenzae cases reported were the non-typeable strain also seen at the national level.  Most cases of Haemophilus influenzae occur in older adults with other underlying conditions that make them susceptible to Haemophilus influenzae. 

For more data about this condition, view our Infectious Disease Annual Reports or submit a Data Request.  

Table I. Reported Haemophilus influenzae, invasive Disease and Reported Disease Rates - Texas, 2014-2023

¹ Cases per 100,000 population. Population data for years 2014-2018 is from the Department of State Health Services, Center for Health Statistics. Population data for 2019-2023 is projected

population from Texas Demographic Center’s Texas Populations Projections Program and updated on July 18, 2019. For years 2014 (27,470,110), 2015 (27,695,284),

2016 (28,240,245), 2017 (28,797,290), 2018 (29,366,479), 2019 (29,193,268), 2020 (29,677,668), 2021 (30,168,926), 2022 (30,667,390), and 2023 (31,172,832)

projected population was used.

Additional case data can be found in the Texas Annual Reports