California is in the throes of a whooping cough epidemic, state health department officials announced Friday. 
 
 Dr. Ron Chapman, director of the California Department of Public Health, said 3,458 cases of whooping cough have been reported since Jan. 1 -- including 800 in the past two weeks. That total is more than all the cases reported in 2013. 
 
 "Preventing severe disease and death in infants is our highest priority," Chapman said in a statement. "We urge all pregnant women to get vaccinated. We also urge parents to vaccinate infants as soon as possible." 
 
 Whooping cough, or pertussis, is cyclical and peaks every three to five years. The last peak in California occurred in 2010, when a total of 9,159 cases were reported. Chapman said it is likely another peak is underway. 
 
 Health department officials say infants too young to be fully immunized remain most vulnerable to severe and fatal cases of pertussis. Two-thirds of pertussis hospitalizations have been in children four months or younger. Two infant deaths have been reported. 
 
 The Tdap vaccination for pregnant women is the best way to protect infants who are too young to be vaccinated, health officials say. 
 
 All pregnant women should be vaccinated with Tdap in the third trimester of each pregnancy, regardless of previous Tdap vaccination. In addition, infants should be vaccinated as soon as possible. The first dose of pertussis vaccine can be given as early as 6 weeks of age. 
 
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 Older children, pre-adolescents, and adults also should also be vaccinated against pertussis according to current recommendations. It is particularly important that persons who will be around newborns also be vaccinated. 
 
 "Unlike some other vaccine-preventable diseases, like measles, neither vaccination nor illness from pertussis offers lifetime immunity," said Chapman. "However, vaccination is still the best defense against this potentially fatal disease." 
 
 Symptoms of pertussis vary by age. For children, a typical case of pertussis starts with a cough and runny nose for one to two weeks. The cough then worsens and children may have rapid coughing spells that end with a "whooping" sound. 
 
 Young infants may not have typical pertussis symptoms and may have no apparent cough. Parents may describe episodes in which the infant's face turns red or purple. For adults, pertussis may simply be a cough that persists for several weeks. 
 
 Contact Tracy Seipel at 408-920-5343. Follow her at Twitter.com/taseipel. 

 Story highlights California handles 800 cases of whooping cough in two weeks 
 
 Health department: This is a problem of 'epidemic proportions" 
 
 Whooping cough, or pertussis, is highly contagious 
 
 California is being hit hard with a whooping cough epidemic, according to the state's public health department , with 800 cases reported in the past two weeks alone. 
 
 The agency says that there were 3,458 whooping cough cases reported between January 1 and June 10, well ahead of the number of cases reported for all of 2013. 
 
 This is a problem of "epidemic proportions," the department said. And the number of actual cases may be even higher, because past studies have shown that for every case of whooping cough that is reported, there are 10 more that are not officially counted. 
 
 Whooping cough , known to doctors as pertussis , is a highly contagious respiratory infection that is caused by a bacterium known as Bordetella pertussis. 
 
 The popular name for the disease comes from the whooping sound an infected person makes when gasping for breath after a coughing fit. 
 
 The bacteria spreads through coughing and sneezing. One person can infect up to 15 people nearby, according to the Centers for Disease Control and Prevention. Typically symptoms appear an average of seven to 10 days after exposure. 
 
 Infants and young children are more vulnerable to the disease than other age groups. It can be particularly dangerous for babies. About half of the infants who get whooping cough end up in a hospital. Some cases are fatal. 
 
 That's why the public health department in California is strongly urging people to make sure their vaccinations are up to date, especially if they're pregnant. State health officials are working closely with schools and local health departments to spread the word. 
 
 "Unlike some other vaccine-preventable diseases like measles, neither vaccination nor illness from pertussis offers lifetime immunity," Dr. Ron Chapman, director of the California Department of Public Health, said in a statement. "However, vaccination is still the best defense against the potentially fatal diseases." 
 
 All adults should get a Tdap booster, unless you had one as a teenager (after age 11). 
 
 Nationally, more than 90% of children get the first three doses of the vaccine, but far fewer get the booster. 
 
 California has historically had higher vaccination rates than other states, but a recent study found large clusters of parents who did not vaccinate their children close to areas with a large number of whooping cough cases during the 2010 California outbreak 
 
 The current outbreak is too new for scientists to know if there is a similar pattern. 
 
 Whooping cough cases have spread rapidly in the United States this year, with a 24% increase nationally in the number of cases, compared to January through April of last year, according to the CDC 
 
 Other states are reporting similar problems. The Mobile County Health Department in Alabama, for example, recently noted an "alarming" rise of cases locally, with 18 cases in May and June. That's more than all the reported cases in Mobile for 2013, health officials say. 
 
 If you do catch whooping cough, you will typically be treated with antibiotics. Doctors often also treat all the family members in an infected person's house to prevent transmission.
– At least 3,458 cases of whooping cough have been reported in California this year—more than the number reported through all of last year. Facing 800 cases in the past two weeks, the state has now declared an epidemic, the San Jose Mercury News reports. "We urge all pregnant women to get vaccinated," says state public health director Ron Chapman. "We also urge parents to vaccinate infants as soon as possible." Though it doesn't offer lifetime immunity, "vaccination is still the best defense against this potentially fatal disease," he notes. Adults should generally receive booster shots against the disease, CNN notes; the Mercury News cites a special risk to those who spend time around infants. The bacterial infection, also called pertussis, may begin with coughing and a runny nose in children. After a week or two, coughing may finish with a "whoop" sound. The greatest danger is to infants too young to receive full immunization, officials say. In California, two babies have died, and two-thirds of cases have been in kids four months old or younger. The highly contagious disease has increased 24% nationwide this year compared to the period from January to April 2013, CNN notes.