With more than 800 new cases reported in just the last two weeks, California has officially reached “epidemic proportions” of whooping cough (pertussis). Typically the state sees 80 to 100 cases a month. Babies are the most vulnerable.

As of June 10, there have been 3,458 cases reported to the California Department of Public Health (CDPH). That’s more than the number of reports for all of 2013, not to mention summer months are usually the worst.

Two-thirds of pertussis hospitalizations have been in children four months or younger, and two infant deaths have already been reported. “We urge all pregnant women to get vaccinated,” CDPH director Ron Chapman says in a statement. “We also urge parents to vaccinate infants as soon as possible.” That also goes for anyone who expects to be around newborns.

The first dose of the pertussis vaccine can be given when an infant reaches 6 weeks of age. Infants who are too young to be immunized, however, remain the most vulnerable to severe and fatal cases. All pregnant women, the department urges, should be vaccinated with Tdap in their third trimester for each pregnancy -- the immunity will transfer to the baby, at least temporarily.

To be clear, whooping cough hasn’t been declared a public health emergency. When a disease exceeds anticipated levels, that’s when it’s considered an epidemic, according to CDPH’s Gil Chavez.

Whooping cough is cyclical and peaks every three to five years. California’s last peak was in 2010 -- with 9,163 cases -- so officials expect another is underway. On the national level, between January 1 and April 14 of this year, 4,838 cases have been reported to the U.S. Centers for Disease Control and Prevention (CDC) by 48 states and Washington, D.C. That’s a 24 percent increase compared with the same time period last year (mapped above).

The disease is caused by the Bordetella pertussis bacterium, which clings to the little hairs that line our airways. They produce toxins that stop the hairs from sweeping the airways clean -- inflaming the surrounding tissue and causing constriction from mucus.

Symptoms varying by age. In adults, it may just be a persistent cough. For children, a typical case starts with a cough and a runny nose for up to two weeks and is followed by rapid coughing spells that end with a “whooping” sound. Young infants may have no apparent cough, though parents have described episodes of their infant’s face turning red or purple.

Having had the illness or the vaccine doesn’t mean you have lifetime immunity. “However, vaccination is still the best defense against this potentially fatal disease,” Chapman says.

The CDPH released the latest pertussis report [pdf] last week. All summary reports are available here.

[CDPH via Los Angeles Times]

Image: CDC